PHP 7.0.6 Released

    Anonymous functions

    Anonymous functions, also known as closures, allow the creation of functions which have no specified name. They are most useful as the value of callback parameters, but they have many other uses.

    Example #1 Anonymous function example

    <?php
    echo preg_replace_callback('~-([a-z])~', function ($match) {
        return     strtoupper($match[1]);
    },     'hello-world');
    // outputs helloWorld
    ?>

    Closures can also be used as the values of variables; PHP automatically converts such expressions into instances of the Closure internal class. Assigning a closure to a variable uses the same syntax as any other assignment, including the trailing semicolon:

    Example #2 Anonymous function variable assignment example

    <?php
    $greet     = function($name)
    {
            printf("Hello %s\r\n", $name);
    };

    $greet('World');
    $greet('PHP');
    ?>

    Closures may also inherit variables from the parent scope. Any such variables must be passed to the use language construct.

    Example #3 Inheriting variables from the parent scope

    <?php
    $message     = 'hello';

    // No "use"
    $example = function () {
            var_dump($message);
    };
    $example();

    // Inherit $message
    $example = function () use ($message) {
            var_dump($message);
    };
    $example();

    // Inherited variable's value is from when the function
    // is defined, not when called
    $message = 'world';
    $example();

    // Reset message
    $message = 'hello';

    // Inherit by-reference
    $example = function () use (&$message) {
            var_dump($message);
    };
    $example();

    // The changed value in the parent scope
    // is reflected inside the function call
    $message = 'world';
    $example();

    // Closures can also accept regular arguments
    $example = function ($arg) use ($message) {
            var_dump($arg . ' ' . $message);
    };
    $example("hello");
    ?>

    The above example will output something similar to:

    Notice: Undefined variable: message in /example.php on line 6
NULL
string(5) "hello"
string(5) "hello"
string(5) "hello"
string(5) "world"
string(11) "hello world"

    Inheriting variables from the parent scope is not the same as using global variables. Global variables exist in the global scope, which is the same no matter what function is executing. The parent scope of a closure is the function in which the closure was declared (not necessarily the function it was called from). See the following example:

    Example #4 Closures and scoping

    <?php
    // A basic shopping cart which contains a list of added products
    // and the quantity of each product. Includes a method which
    // calculates the total price of the items in the cart using a
    // closure as a callback.
    class Cart
    {
        const     PRICE_BUTTER  = 1.00;
        const     PRICE_MILK    = 3.00;
        const     PRICE_EGGS    = 6.95;

        protected     $products = array();
        
        public function     add($product, $quantity)
        {
                $this->products[$product] = $quantity;
        }
        
        public function     getQuantity($product)
        {
            return isset(    $this->products[$product]) ? $this->products[$product] :
                       FALSE;
        }
        
        public function     getTotal($tax)
        {
                $total = 0.00;
            
                $callback =
                function (    $quantity, $product) use ($tax, &$total)
                {
                        $pricePerItem = constant(__CLASS__ . "::PRICE_" .
                            strtoupper($product));
                        $total += ($pricePerItem * $quantity) * ($tax + 1.0);
                };
            
                array_walk($this->products, $callback);
            return     round($total, 2);
        }
    }

    $my_cart = new Cart;

    // Add some items to the cart
    $my_cart->add('butter', 1);
    $my_cart->add('milk', 3);
    $my_cart->add('eggs', 6);

    // Print the total with a 5% sales tax.
    print $my_cart->getTotal(0.05) . "\n";
    // The result is 54.29
    ?>

    Anonymous functions are implemented using the Closure class.

    Changelog

    Version Description
    5.4.0 $this can be used in anonymous functions.
    5.3.0 Anonymous functions become available.

    Notes

    Note: It is possible to use func_num_args(), func_get_arg(), and func_get_args() from within a closure.

    User Contributed Notes

    orls
    5 years ago
    Watch out when 'importing' variables to a closure's scope  -- it's easy to miss / forget that they are actually being *copied* into the closure's scope, rather than just being made available.

    So you will need to explicitly pass them in by reference if your closure cares about their contents over time:

    <?php
    $result     = 0;

    $one = function()
    {     var_dump($result); };

    $two = function() use ($result)
    {     var_dump($result); };

    $three = function() use (&$result)
    {     var_dump($result); };

    $result++;

    $one();    // outputs NULL: $result is not in scope
    $two();    // outputs int(0): $result was copied
    $three();    // outputs int(1)
    ?>

    Another less trivial example with objects (what I actually tripped up on):

    <?php
    //set up variable in advance
    $myInstance = null;

    $broken = function() uses ($myInstance)
    {
        if(!empty(    $myInstance)) $myInstance->doSomething();
    };

    $working = function() uses (&$myInstance)
    {
        if(!empty(    $myInstance)) $myInstance->doSomething();
    }

    //$myInstance might be instantiated, might not be
    if(SomeBusinessLogic::worked() == true)
    {
            $myInstance = new myClass();
    }

    $broken();    // will never do anything: $myInstance will ALWAYS be null inside this closure.
    $working();    // will call doSomething if $myInstance is instantiated

    ?>
    mike at blueroot dot co dot uk
    6 years ago
    To recursively call a closure, use this code.

    <?php
    $recursive     = function () use (&$recursive){
            // The function is now available as $recursive
    }
    ?>

    This DOES NOT WORK

    <?php
    $recursive     = function () use ($recursive){
            // The function is now available as $recursive
    }
    ?>
    erolmon dot kskn at gmail dot com
    10 months ago
    <?php
            /*
        (string) $name Name of the function that you will add to class.
        Usage : $Foo->add(function(){},$name);
        This will add a public function in Foo Class.
        */
            class Foo
            {
            public function     add($func,$name)
            {
                    $this->{$name} = $func;
            }
            public function     __call($func,$arguments){
                    call_user_func_array($this->{$func}, $arguments);
            }
        }
            $Foo = new Foo();
            $Foo->add(function(){
            echo     "Hello World";
        },    "helloWorldFunction");
            $Foo->add(function($parameterone){
            echo     $parameterone;
        },    "exampleFunction");
            $Foo->helloWorldFunction(); /*Output : Hello World*/
            $Foo->exampleFunction("Hello PHP"); /*Output : Hello PHP*/
    ?>
    fabiolimasouto at gmail dot com
    5 years ago
    You may have been disapointed if you tried to call a closure stored in an instance variable as you would regularly do with methods:

    <?php

    $obj     = new StdClass();

    $obj->func = function(){
    echo     "hello";
    };

    //$obj->func(); // doesn't work! php tries to match an instance method called "func" that is not defined in the original class' signature

    // you have to do this instead:
    $func = $obj->func;
    $func();

    // or:
    call_user_func($obj->func);

    // however, you might wanna check this out:
    $array['func'] = function(){
    echo     "hello";
    };

    $array['func'](); // it works! i discovered that just recently ;)
    ?>

    Now, coming back to the problem of assigning functions/methods "on the fly" to an object and being able to call them as if they were regular methods, you could trick php with this lawbreaker-code:

    <?php
    class test{
    private     $functions = array();
    private     $vars = array();

    function     __set($name,$data)
    {
      if(    is_callable($data))
            $this->functions[$name] = $data;
      else
           $this->vars[$name] = $data;
    }

    function     __get($name)
    {
      if(isset(    $this->vars[$name]))
       return     $this->vars[$name];
    }

    function     __call($method,$args)
    {
      if(isset(    $this->functions[$method]))
      {
           call_user_func_array($this->functions[$method],$args);
      } else {
           // error out
          }
    }
    }

    // LET'S BREAK SOME LAW NOW!
    $obj = new test;

    $obj->sayHelloWithMyName = function($name){
    echo     "Hello $name!";
    };

    $obj->sayHelloWithMyName('Fabio'); // Hello Fabio!

    // THE OLD WAY (NON-CLOSURE) ALSO WORKS:

    function sayHello()
    {
    echo     "Hello!";
    }

    $obj->justSayHello = 'sayHello';
    $obj->justSayHello(); // Hello!
    ?>

    NOTICE: of course this is very bad practice since you cannot refere to protected or private fields/methods inside these pseudo "methods" as they are not instance methods at all but rather ordinary functions/closures assigned to the object's instance variables "on the fly". But I hope you've enjoyed the jurney ;)
    housni dot yakoob at gmail dot com
    6 years ago
    If you want to make sure that one of the parameters of your function is a Closure, you can use Type Hinting.
    see: http://php.net/manual/en/language.oop5.typehinting.php

    Example:
    <?php

    class TheRoot
    {
        public function     poidh($param) {
            echo     "TheRoot $param!";
        }  

    }

    class     Internet
    {
            # here, $my_closure must be of type object Closure
            public function run_my_closure($bar, Closure $my_closure) {
                $my_closure($bar);
        }  
    }

    $Internet = new Internet();
    $Root = new TheRoot();

    $Internet->run_my_closure($Root, function($Object) {
            $Object->poidh(42);
    });

    ?>
    The above code simply yields:
    "TheRoot 42!"

    NOTE: If you are using namespaces, make sure you give a fully qualified namespace.

    print_r() of Internet::run_my_closure's $my_closure
    <?php
    Closure Object
    (
        [    parameter] => Array
            (
                [    $Object] =>
            )

    )
    ?>

    var_dump() of Internet::run_my_closure's $my_closure
    <?php
    object    (Closure)#3 (1) {
          ["parameter"]=>
      array(    1) {
        [    "$Object"]=>
            string(10) ""
          }
    }
    ?>
    simon at generalflows dot com
    4 years ago
    <?php

    /*
    * An example showing how to use closures to implement a Python-like decorator
    * pattern.
    *
    * My goal was that you should be able to decorate a function with any
    * other function, then call the decorated function directly:
    *
    * Define function:         $foo = function($a, $b, $c, ...) {...}
    * Define decorator:        $decorator = function($func) {...}
    * Decorate it:             $foo = $decorator($foo)
    * Call it:                 $foo($a, $b, $c, ...)
    *
    * This example show an authentication decorator for a service, using a simple
    * mock session and mock service.
    */

    session_start();

    /*
    * Define an example decorator. A decorator function should take the form:
    * $decorator = function($func) {
    *     return function() use $func) {
    *         // Do something, then call the decorated function when needed:
    *         $args = func_get_args($func);
    *         call_user_func_array($func, $args);
    *         // Do something else.
    *     };
    * };
    */
    $authorise = function($func) {
        return function() use (    $func) {
            if (    $_SESSION['is_authorised'] == true) {
                    $args = func_get_args($func);
                    call_user_func_array($func, $args);
            }
            else {
                echo     "Access Denied";
            }
        };
    };

    /*
    * Define a function to be decorated, in this example a mock service that
    * need to be authorised.
    */
    $service = function($foo) {
        echo     "Service returns: $foo";
    };

    /*
    * Decorate it. Ensure you replace the origin function reference with the
    * decorated function; ie just $authorise($service) won't work, so do
    * $service = $authorise($service)
    */
    $service = $authorise($service);

    /*
    * Establish mock authorisation, call the service; should get
    * 'Service returns: test 1'.
    */
    $_SESSION['is_authorised'] = true;
    $service('test 1');

    /*
    * Remove mock authorisation, call the service; should get 'Access Denied'.
    */
    $_SESSION['is_authorised'] = false;
    $service('test 2');

    ?>
    cHao
    2 years ago
    In case you were wondering (cause i was), anonymous functions can return references just like named functions can.  Simply use the & the same way you would for a named function...right after the `function` keyword (and right before the nonexistent name).

    <?php
        $value     = 0;
            $fn = function &() use (&$value) { return $value; };

            $x =& $fn();
            var_dump($x, $value);        // 'int(0)', 'int(0)'
            ++$x;
            var_dump($x, $value);        // 'int(1)', 'int(1)'
    aaron at afloorabove dot com
    6 years ago
    Anonymous functions are great for events!

    <?php

    class Event {

      public static     $events = array();
     
      public static function     bind($event, $callback, $obj = null) {
        if (!    self::$events[$event]) {
              self::$events[$event] = array();
        }
       
            self::$events[$event][] = ($obj === null)  ? $callback : array($obj, $callback);
      }
     
      public static function     run($event) {
        if (!    self::$events[$event]) return;
       
        foreach (    self::$events[$event] as $callback) {
          if (    call_user_func($callback) === false) break;
        }
      }

    }

    function     hello() {
      echo     "Hello from function hello()\n";
    }

    class     Foo {
      function     hello() {
        echo     "Hello from foo->hello()\n";
      }
    }

    class     Bar {
      function     hello() {
        echo     "Hello from Bar::hello()\n";
      }
    }

    $foo = new Foo();

    // bind a global function to the 'test' event
    Event::bind("test", "hello");

    // bind an anonymous function
    Event::bind("test", function() { echo "Hello from anonymous function\n"; });

    // bind an class function on an instance
    Event::bind("test", "hello", $foo);

    // bind a static class function
    Event::bind("test", "Bar::hello");

    Event::run("test");

    /* Output
    Hello from function hello()
    Hello from anonymous function
    Hello from foo->hello()
    Hello from Bar::hello()
    */

    ?>
    Hayley Watson
    5 years ago
    As an alternative to gabriel's recursive construction, you may instead assign the recursive function to a variable, and use it by reference, thus:

    <?php
    $fib     = function($n)use(&$fib)
    {
        if(    $n == 0 || $n == 1) return 1;
        return     $fib($n - 1) + $fib($n - 2);
    };

    echo     $fib(10);
    ?>
    Hardly a sensible implementation of the Fibonacci sequence, but that's not the point! The point is that the variable needs to be used by reference, not value.

    Without the '&', the anonymous function gets the value of $fib at the time the function is being created. But until the function has been created, $fib can't have it as a value! It's not until AFTER the function has been assigned to $fib that $fib can be used to call the function - but by then it's too late to pass its value to the function being created!

    Using a reference resolves the dilemma: when called, the anonymous function will use $fib's current value, which will be the anonymous function itself.

    At least, it will be if you don't reassign $fib to anything else between creating the function and calling it:

    <?php
    $fib     = function($n)use(&$fib)
    {
        if(    $n == 0 || $n == 1) return 1;
        return     $fib($n - 1) + $fib($n - 2);
    };

    $lie = $fib;

    $fib = function($n)
    {
        return     100;
    };

    echo     $lie(10); // 200, because $fib(10 - 1) and $fib(10 - 2) both return 100.
    ?>

    Of course, that's true of any variable: if you don't want its value to change, don't change its value.

    All the usual scoping rules for variables still apply: a local variable in a function is a different variable from another one with the same name in another function:

    <?php
    $fib     = function($n)use(&$fib)
    {
        if(    $n == 0 || $n == 1) return 1;
        return     $fib($n - 1) + $fib($n - 2);
    };

    $bark = function($f)
    {
            $fib = 'cake';    // A totally different variable from the $fib above.
            return 2 * $f(5);
    };

    echo     $bark($fib); // 16, twice the fifth Fibonacci number

    ?>
    gabriel dot totoliciu at ddsec dot net
    5 years ago
    If you want to make a recursive closure, you will need to write this:

    $some_var1="1";
    $some_var2="2";

    function($param1, $param2) use ($some_var1, $some_var2)
    {

    //some code here

    call_user_func(__FUNCTION__, $other_param1, $other_param2);

    //some code here

    }

    If you need to pass values by reference you should check out

    http://www.php.net/manual/en/function.call-user-func.php
    http://www.php.net/manual/en/function.call-user-func-array.php

    If you're wondering if $some_var1 and $some_var2 are still visible by using the call_user_func, yes, they are available.
    kdelux at gmail dot com
    5 years ago
    Here is an example of one way to define, then use the variable ( $this ) in Closure functions.  The code below explores all uses, and shows restrictions.

    The most useful tool in this snippet is the requesting_class() function that will tell you which class is responsible for executing the current Closure(). 

    Overview:
    -----------------------
    Successfully find calling object reference.
    Successfully call $this(__invoke);
    Successfully reference $$this->name;
    Successfully call call_user_func(array($this, 'method'))

    Failure: reference anything through $this->
    Failure: $this->name = '';
    Failure: $this->delfect();

    <?php

       
       
            function requesting_class()
        {
            foreach(    debug_backtrace(true) as $stack){
                if(isset(    $stack['object'])){
                    return     $stack['object'];
                }
            }
           
        }
       
           
       
       
       
       
        class     Person
            {
            public     $name = '';
            public     $head = true;
            public     $feet = true;
            public     $deflected = false;
           
            function     __invoke($p){ return $this->$p; }
            function     __toString(){ return 'this'; } // test for reference
           
                function __construct($name){ $this->name = $name; }
            function     deflect(){ $this->deflected = true; }
           
            public function     shoot()
            {     // If customAttack is defined, use that as the shoot resut.  Otherwise shoot feet
                    if(is_callable($this->customAttack)){
                    return     call_user_func($this->customAttack);
                }
               
                    $this->feet = false;
            }
        }

            $p = new Person('Bob');

       
            $p->customAttack =
                    function(){
                       
                        echo     $this; // Notice: Undefined variable: this
                       
                        #$this = new Class() // FATAL ERROR
                       
                        // Trick to assign the variable '$this'
                            extract(array('this' => requesting_class())); // Determine what class is responsible for making the call to Closure
                       
                            var_dump( $this  );  // Passive reference works
                            var_dump( $$this ); // Added to class:  function __toString(){ return 'this'; }
                       
                            $name = $this('name'); // Success
                            echo $name;            // Outputs: Bob
                            echo '<br />';
                        echo $    $this->name;
                       
                            call_user_func_array(array($this, 'deflect'), array()); // SUCCESSFULLY CALLED
                       
                        #$this->head = 0; //** FATAL ERROR: Using $this when not in object context
                            $$this->head = 0;  // Successfully sets value
                       
                        };

            print_r($p);
       
            $p->shoot();
       
            print_r($p);

       
        die();

    ?>
    orwellophile at phpblue dot net
    4 years ago
    You can create a dynamic method with a class, with access to member variables, with a little bit of trickery:

    <?
        class DynamicFunction {
            var $functionPointer;
            var $mv = "The Member Variable";

            function __construct() {
                $this->functionPointer = function($arg) {
                    return sprintf("I am the default closure, argument is %s\n", $arg);
                };
            }

            function changeFunction($functionSource) {
                $functionSource = str_replace('$this', '$_this', $functionSource);
                $_this = clone $this;

                $f = '$this->functionPointer = function($arg) use ($_this) {' . PHP_EOL;
                $f.= $functionSource . PHP_EOL . "};";
                eval($f);
            }

            function __call($method, $args) {
                if ( $this->{$method} instanceof Closure ) {
                    return call_user_func_array($this->{$method},$args);
                } else {
                    throw new Exception("Invalid Function");
                }
            }
        }

        if (!empty($argc) && !strcmp(basename($argv[0]), basename(__FILE__))) {
            $dfstring1 = 'return sprintf("I am dynamic function 1, argument is %s, member variables is %s\n", $arg, $this->mv);';
            $dfstring2 = 'return sprintf("I am dynamic function 2, argument is %s, member variables is %s\n", $arg, $this->mv);';

            $df = new DynamicFunction();
            $df->changeFunction($dfstring1);
            echo $df->functionPointer("Rabbit");

            $df->changeFunction($dfstring2);
            $df->mv = "A different var";
            echo $df->functionPointer("Cow");
        };
    ?>
    martin dot partel at gmail dot com
    5 years ago
    $this is currently (PHP 5.3.2) not usable directly with closures.

    One can write:
    <?php
    $self     = $this;
    function () use (    $self) { ... }
    ?>
    but then the private/protected members of $this cannot be used inside the closure. This makes closures much less useful in OO code.

    Until this is fixed, one can cheat using reflection:
    <?php
    class FullAccessWrapper
    {
        protected     $_self;
        protected     $_refl;
       
        public function     __construct($self)
        {
                $this->_self = $self;
                $this->_refl = new ReflectionObject($self);
        }
       
        public function     __call($method, $args)
        {
                $mrefl = $this->_refl->getMethod($method);
                $mrefl->setAccessible(true);
            return     $mrefl->invokeArgs($this->_self, $args);
        }
       
        public function     __set($name, $value)
        {
                $prefl = $this->_refl->getProperty($name);
                $prefl->setAccessible(true);
                $prefl->setValue($this->_self, $value);
        }
       
        public function     __get($name)
        {
                $prefl = $this->_refl->getProperty($name);
                $prefl->setAccessible(true);
            return     $prefl->getValue($this->_self);
        }
       
        public function     __isset($name)
        {
                $value = $this->__get($name);
            return isset(    $value);
        }
    }

    /**
    * Usage:
    * $self = giveAccess($this);
    * function() use ($self) { $self->privateMember... }
    */
    function giveAccess($obj)
    {
        return new     FullAccessWrapper($obj);
    }

    // Example:

    class Foo
    {
        private     $x = 3;
        private function     f()
        {
            return     15;
        }
       
        public function     getClosureUsingPrivates()
        {
                $self = giveAccess($this);
            return function () use (    $self) {
                return     $self->x * $self->f();
            };
        }
    }

    $foo = new Foo();
    $closure = $foo->getClosureUsingPrivates();
    echo     $closure() . "\n"; // Prints 45 as expected
    ?>
    mail at mkharitonov dot net
    2 years ago
    Some comparisons of PHP and JavaScript closures.

    === Example 1 (passing by value) ===
    PHP code:
    <?php
    $aaa     = 111;
    $func = function() use($aaa){ print $aaa; };
    $aaa = 222;
    $func(); // Outputs "111"
    ?>

    Similar JavaScript code:
    <script type="text/javascript">
    var aaa = 111;
    var func = (function(aaa){ return function(){ alert(aaa); } })(aaa);
    aaa = 222;
    func(); // Outputs "111"
    </script>

    Be careful, following code is not similar to previous code:
    <script type="text/javascript">
    var aaa = 111;
    var bbb = aaa;
    var func = function(){ alert(bbb); };
    aaa = 222;
    func(); // Outputs "111", but only while "bbb" is not changed after function declaration

    // And this technique is not working in loops:
    var functions = [];
    for (var i = 0; i < 2; i++)
    {
        var i2 = i;
        functions.push(function(){ alert(i2); });
    }
    functions[0](); // Outputs "1", wrong!
    functions[1](); // Outputs "1", ok
    </script>

    === Example 2 (passing by reference) ===
    PHP code:
    <?php
    $aaa     = 111;
    $func = function() use(&$aaa){ print $aaa; };
    $aaa = 222;
    $func(); // Outputs "222"
    ?>

    Similar JavaScript code:
    <script type="text/javascript">
    var aaa = 111;
    var func = function(){ alert(aaa); };
    aaa = 222; // Outputs "222"
    func();
    </script>
    a dot schaffhirt at sedna-soft dot de
    6 years ago
    When using anonymous functions as properties in Classes, note that there are three name scopes: one for constants, one for properties and one for methods. That means, you can use the same name for a constant, for a property and for a method at a time.

    Since a property can be also an anonymous function as of PHP 5.3.0, an oddity arises when they share the same name, not meaning that there would be any conflict.

    Consider the following example:

    <?php
            class MyClass {
            const     member = 1;
           
            public     $member;
           
            public function     member () {
                return     "method 'member'";
            }
           
            public function     __construct () {
                    $this->member = function () {
                    return     "anonymous function 'member'";
                };
            }
        }
       
            header("Content-Type: text/plain");
       
            $myObj = new MyClass();

            var_dump(MyClass::member);  // int(1)
            var_dump($myObj->member);   // object(Closure)#2 (0) {}
            var_dump($myObj->member()); // string(15) "method 'member'"
            $myMember = $myObj->member;
            var_dump($myMember());      // string(27) "anonymous function 'member'"
    ?>

    That means, regular method invocations work like expected and like before. The anonymous function instead, must be retrieved into a variable first (just like a property) and can only then be invoked.

    Best regards,
    mike at borft dot student dot utwente dot nl
    4 years ago
    Since it is possible to assign closures to class variables, it is a shame it is not possible to call them directly. ie. the following does not work:
    <?php
    class foo {

      public     test;

      public function     __construct(){
            $this->test = function($a) {
          print     "$a\n";
        };
      }
    }

    $f = new foo();

    $f->test();
    ?>

    However, it is possible using the magic __call function:
    <?php
    class foo {

      public     test;

      public function     __construct(){
            $this->test = function($a) {
          print     "$a\n";
        };
      }

      public function     __call($method, $args){
        if (     $this->{$method} instanceof Closure ) {
          return     call_user_func_array($this->{$method},$args);
        } else {
          return     parent::__call($method, $args);
        }
      }
    }
    $f = new foo();
    $f->test();
    ?>
    it
    Hope it helps someone ;)
    reinaldorock at yahoo dot com dot br
    4 years ago
    Using closure to encapsulate environment
    <?php
        $fib     = function($n) use(&$fib) {
            if(    $n == 0 || $n == 1) return 1;
            return     $fib($n - 1) + $fib($n - 2);
        };

       echo     $fib(2) . "\n"; // 2
           $lie = $fib;
           $fib = function(){die('error');};//rewrite $fib variable
           echo $lie(5); // error   because $fib is referenced by closure

    ?>

    Alternative Fibonacci implementation using a self called function like javascript to encapsulate references variables.

    <?php
    $fib     = call_user_func(function(){
      
            $fib = function($n) use(&$fib) {
            if(    $n == 0 || $n == 1) return 1;
            return     $fib($n - 1) + $fib($n - 2);
        };

        return     $fib;
    });

    echo     $fib(2) . "\n";//2
    $ok = $fib;

    $fib = function(){die('error')};//rewrite $fib variable but don't referenced $fib used by closure
    echo $ok(5);//result ok
    ?>
    alexander at cheprasov dot com
    2 years ago
    Example:

    <?php
    $a     = 213;

    $f = function() use ($a){
        echo     $a;
    };

    $a = 144;
    echo     $a;

    $f();
    ?>

    Result:
    144
    213
    anonymous
    5 years ago
    Base dao class illustrating the usefulness of closures.
    * Handles opening and closing of connections.
    * Adds slashes sql
    * Type checking of sql parameters and casts as appropriate
    * Provides hook for processing of result set and emitting one or more objects.
    * Provides hook for accessing underlying link and result objects.

    <?php

    define    ("userName","root");
    define("password","root");
    define("dbName","ahcdb");
    define("hostName","localhost");

    class     BaseDao {

        function     getConnection()    {
                $link = mysql_connect(hostName, userName, password);
            if (!    $link)
                die(    "Could not connect: " . mysql_error());
            if (!    mysql_select_db(dbName))
                die(    "Could not select database: " . mysql_error());
            return     $link;
        }
       
        function     setParams(& $sql, $params)    {
            if(    $params != null)
                    $sql = vsprintf($sql, array_map(function($n) {
                    if(    is_int($n))
                        return (int)    $n;
                    if(    is_float($n))
                        return (float)    $n;
                    if(    is_string($n))
                        return     "'".mysql_real_escape_string($n)."'";
                    return     mysql_real_escape_string($n);
                },     $params));
        }

        function     executeQuery($sql, $params, $callback = null)    {
                $link  = $this->getConnection();
                $this->setParams($sql, $params);
                $return = null;
            if((    $result = mysql_query($sql, $link)) != null)
                if(    $callback != null)
                        $return = $callback($result, $link);
            if(    $link != null)
                    mysql_close($link);
            if(!    $result)
                die(    "Fatal Error: Invalid query '$sql' : " . mysql_error());
            return     $return;
        }

        function     getList($sql, $params, $callback)    {
            return     $this->executeQuery($sql, $params, function($result, $link) use ($callback) {
                    $idx = 0;
                    $list = array();
                while (    $row = mysql_fetch_assoc($result))
                    if(    $callback != null)
                            $list[$idx] = $callback($idx++, $row);
                return     $list;
            });
        }
       
        function     getSingle($sql, $params, $callback)    {
            return     $this->executeQuery($sql, $params, function($result, $link) use ($callback) {
                if (    $row = mysql_fetch_assoc($result))
                        $obj = $callback($row);
                return     $obj;
            });
        }
    }

    class     Example    {
        var     $id;
        var     $name;
       
        function     Example($id, $name){
                $this->id = $id;
                $this->name = $name;
        }
       
        function     setId($id){
                $this->id = $id;
        }
    }

    class     ExampleDao extends BaseDao    {
       
       
        function     getAll(){
            return     parent::getList("select * from nodes", null, function($idx, $row) {
                return new     Example($row["id"], $row["name"]);
            });
        }
       
        function     load($id){
            return     parent::getSingle("select * from nodes where id = %1\$s", array($id), function($row) {
                return new     Example($row["id"], $row["name"]);
            });
        }
       
        function     update($example){
            return     parent::executeQuery("update nodes set name = '' where  id = -1", null, function($result, $link){
                return     $result;
            });
        }
       
        function     insert(& $example){
            return     parent::executeQuery("insert into nodes", null, function($result, $link) use ($example){
                    $id = mysql_insert_id($link);
                    $example->setId($id);
                return     $result;
            });
        }   
    }

    $exampleDao = new ExampleDao();

    $list = $exampleDao->getAll());

    $exampleObject = $exampleDao->load(1));

    $exampleDao->update($exampleObject);

    ?>
    andris at codeaid dot net
    2 years ago
    Haven't seen it documented anywhere but PHP 5.4 now allows accessing private and protected members of an object if it's passed into a lambda function:

    <?php
    class Scope
    {
        protected     $property = 'default';
            // or even
        // private $property = 'default';

            public function run()
        {
                $self = $this;
                $func = function() use ($self) {
                    $self->property = 'changed';
            };

                $func();
                var_dump($this->property);
        }
    }

    $scope = new Scope();
    $scope->run();
    ?>

    When running the file under PHP 5.3 you get the following error message:
    * Fatal error: Cannot access protected property Scope::$property in ./file.php on line 11

    PHP 5.4, however, does not complain and outputs "changed" as expected.

    Not sure why it's like that but I suspect it has something to do with 5.4 supporting passing $this into lambda functions.

    Speaking of which, something to remember is that the following won't work:
    <?php
    $func     = function() use ($this) {
            $this->property = 'changed';
    };
    ?>
    The error you'll get is:
    * PHP Fatal error:  Cannot use $this as lexical variable in ./file.php on line 9

    You have to totally omit the use statement for it to work:
    <?php
    $func     = function() {
            $this->property = 'changed';
    };
    ?>
    assarte dot draven at gmail dot com
    2 years ago
    You cannot use closures as a class variable member in its declaration like this:

    <?php

    class foo
    {
        public     $bar = function() {
            echo     "baz";
        };
    }

    ?>

    I don't know why but this will raise a
    Parse error: syntax error, unexpected 'function' (T_FUNCTION)

    (used PHP 5.4)
    ldrut
    4 years ago
    A common way to avoid contaminating Javascript global space with unneeded variables is to move the code into an immediately called anonymous closure.

    (function(){ ... })()

    The equivalent way to do that in PHP 5.3+ is

    call_user_func(function() use(closure-vars){ ... });
    marcellorvalle at gmail dot com
    3 years ago
    I fell uncomfortable with php's way to pass callbacks ahead. It's just a personal opinion but i think the structure array($object, 'method') a little bit ugly. In some special cases i would like to do something more verbose, like that:

    <?php
        $sortedArray     = ArrayServices::sort($arrayOfPerson, $sortPerson->byName);
    ?>

    Here, "$sortPerson->byName" is a pointer to a function that receives 2 instances of Person and return true if the name of the first is "bigger" than the second. "ArrayServices::sort" is a function that can sort any kind of array using different criterias, it uses the function passed on the second parameter to compare two items on the array

    I am able do that defining a simple abstract class which gives the ability to it's children to expose their methods as closures using __get() magic funtion.

    <?php
    abstract class ClosureExposerObject
    {
        public function     __get($methodName)
        {
            if (    is_callable(
                    array(    $this, $methodName)))
            {
                return function() use (    $methodName)
                {
                        $args = func_get_args();
                    return     call_user_func_array(array($this, $methodName), $args);
                };
            }
            else
            {
                    $className = get_class($this);
                throw new \    BadMethodCallException("$method is not a callable at $className class.");
            }
        }
    }
    ?>

    Now it is possible to define a class SortPerson so that i could use it like in the first code snippet.

    <?php

    class SortPerson extends ClosureExposerObject
    {
        public function     byName(Person p1, Person p2)
        {
            return     p1->getName() > p2->getName();
        }
       
        public function     byAge(Person p1, Person p2)
        {
            return     p1->getAge() > p2->getAge();
        }
       
        public function     bySurName(Person p1, Person p2)
        (...)
    }

    ?>

    I just needed to extend ClosureExposerObject and do nothing more.

    Some observations: SortPerson is a service class but i decided not to implement it with static methods. It is a personal matter but i really dont like to implement such small classes with statics. Also i have inverted some naming conventions (class names as substantives and methods as verbs) but in some very special cases i thing that it actually helps readability.
    varuninorbit at yahoo dot co dot in
    4 months ago
    Here is a simple example to use clousers
    <?php

    function add($x,$y){
        return     $x+$y();   
    }

    echo     add(3,function(){
        return     5;
    });

    ?>

    prints 8
    inaitana
    1 year ago
    Doesn't anyone else think Closure is used here with an inappropriate meaning?

    Isn't closure just the concept of being able to reference the outer function environment from the inner function, as in example #3?

    It's commonly used with anonymous functions, but from what I know it's not the same thing as an anonymous function.
    "Lambda functions" might be another name for anonymous functions, not "Closures".

    I mean, a named function could employ closure too.
    And anonymous functions don't necessarily support closure in all languages.
    jc at jmccc dot com
    2 years ago
    In 5.3, $this cannot be used in an anonymous function, though you can simply assign $this to another variable and pass that into the function in the use section, This quick and dirty hack works for at least calling public functions and accessing public variables of the parent class.

    <?php

    class Example {
        public     $blah;
        function     foo() {
                $that = $this;
                $tmp = function() use ($that) {
                 return     $that->blah;
             }
            return     $tmp;
        }
    }

    $test = new Example();
    $example->blah = "whatever";
    echo     $example->foo(); // prints "whatever"
    derkontrollfreak+9hy5l at gmail dot com
    2 years ago
    Beware that since PHP 5.4 registering a Closure as an object property that has been instantiated in the same object scope will create a circular reference which prevents immediate object destruction:
    <?php

    class Test
    {
        private     $closure;

        public function     __construct()
        {
                $this->closure = function () {
            };
        }

        public function     __destruct()
        {
            echo     "destructed\n";
        }
    }

    new     Test;
    echo     "finished\n";

    /*
    * Result in PHP 5.3:
    * ------------------
    * destructed
    * finished
    *
    * Result since PHP 5.4:
    * ---------------------
    * finished
    * destructed
    */

    ?>

    To circumvent this, you can instantiate the Closure in a static method:
    <?php

    public function __construct()
    {
            $this->closure = self::createClosure();
    }

    public static function     createClosure()
    {
        return function () {
        };
    }

    ?>
    rob at ubrio dot us
    6 years ago
    You can always call protected members using the __call() method - similar to how you hack around this in Ruby using send.

    <?php

    class Fun
    {
    protected function     debug($message)
    {
       echo     "DEBUG: $message\n";
    }

    public function     yield_something($callback)
    {
       return     $callback("Soemthing!!");
    }

    public function     having_fun()
    {
           $self =& $this;
       return     $this->yield_something(function($data) use (&$self)
       {
             $self->debug("Doing stuff to the data");
             // do something with $data
             $self->debug("Finished doing stuff with the data.");
       });
    }

    // Ah-Ha!
    public function __call($method, $args = array())
    {
       if(    is_callable(array($this, $method)))
         return     call_user_func_array(array($this, $method), $args);
    }
    }

    $fun = new Fun();
    echo     $fun->having_fun();

    ?>
    Victor
    2 years ago
    Please note that while You can assign a closure to an array key with the method

    $array['key'] = function() { return $whatever; };

    You cannot do the same with the array assignment operator.

    So

    $array = Array(
      'key' => function() { return $whatever; }
    );

    will NOT work.
    (This is indeed awkward.)
    Anonymous
    6 years ago
    If you want to check whether you're dealing with a closure specifically and not a string or array callback you can do this:

    <?php
    $isAClosure     = is_callable($thing) && is_object($thing);
    ?>
    paul at somewhere dot com
    5 years ago
    I benched instantiating a function and lambda function.

    Functions used:
    <?php

    function data() {
    $var = 'hi';
    }
    $lambda = function() {
    $var = 'hi';
    }

    ?>

    Bench for instantiating a function:
    1.692800000000000082422957 μs
    Bench for instantiating Lambda Function:
    0.906000000000000027533531 μs
    Bench for calling function:
    0.7153000000000000468958206 μs
    Bench for calling lambda function:
    0.6914000000000000145661261 μs

    Calling the lambda function and regular function fluctuates between .81 and .65 so they seem to be the same.
    benkuhl at gmail dot com
    3 years ago
    Beware of scope!  $this refers to the class that the function was defined within.

    ----------- Example #1 - Doesn't work (Notice: Undefined variable: this) -----------
    <?php

    $callableFunc     = function () {
            var_dump($this);
    };

    call_user_func($callableFunc);

    ?>

    ----------- Example #2 - Doesn't work (Notice: Undefined variable: this) -----------
    <?php
    class myClass {
        public function     execute($func) {
            if (    is_callable($func)) {
                    call_user_func($func);
            }
        }
    }

    $class = new myClass();
    $class->execute(function () {
            var_dump($this);
    });
    ?>

    ----------- Example #3 - Works! -----------
    <?php
    class myClass {
        public function     getMyExecutableFunction() {
            return function () {
                    var_dump($this);
            };
        }

        public function     execute($func) {
            if (    is_callable($func)) {
                    call_user_func($func);
            }
        }
    }

    $class = new myClass();
    $class->execute($class->getMyExecutableFunction()); //object(myClass)[1]
    ?>

    $this is not available in a static method!
    mcm dot matt at gmail dot com
    6 years ago
    Example using uasort.

    <?php
    // Usual method.
    function cmp($a, $b) {
        return(    $a > $b);
    }
    uasort($array, 'cmp');

    // New
    uasort($array, function($a, $b) {
        return(    $a > $b);
    });
    ?>
    gerard at visei dot nl
    6 years ago
    The text above the third example tries to explain that anonymous functions can inherit variables from the parent scope, but fails to properly explain how this is done: namely using the "use" keyword in the function definition.

    The following page has a much more detailed explanation of closures in PHP 5.3:
    http://wiki.php.net/rfc/closures
    rmckay at webaware dot com dot au
    2 years ago
    Some hosts are installing the eAccelerator opcode cache with PHP 5.4, and current production versions of this opcode cache break closures. If you find that your nice, working closures break when you load your code to a hosted website, check for eAccelerator (e.g. by calling phpinfo() and checking the output).

    Simple fixes include:

    * disabling eAccelerator and opcode caching
    * replacing eAccelerator with Zend's opcache
    * reverting to PHP 5.3

    Apparently, the eAccelerator project has solved this issue, but hosts move slowly so I recommend removing eAccelerator from the equation for now.
    mrdaniel619 at gmail dot com
    2 years ago
    just in case you ever want to change a member function run time

    <?php

    class t
    {
        var     $num;
       
        var     $dynamic_function;
       
        public function     dynamic_function()
        {
                $func = $this->dynamic_function;
           
                $func($this);
        }
    }

    $p = new t();

    $p->num = 5;

    $p->dynamic_function = function($this_ref) // param cannot be named $this
    {
        echo     $this_ref->num++.'<br />';
    };

    $p->dynamic_function(); // CALL YOUR DYNAMIC FUNCTION

    $p->dynamic_function = function($this_ref) // NEW DYNAMIC fUNCRION
    {
        echo     $this_ref->num.'<br />';
       
            $this_ref->num *= 3;
    };

    $p->dynamic_function(); // CALL DYNAMIC FUNCTION

    echo $p->num; // display number

    exit;

    ?>

    output:
    5
    6
    18
    puskulcu at gmail dot com
    6 years ago
    hello there!
    here is a little code which shows use of the closures as event handlers:

    <?php

          class Button
          {
        public     $OnBeforeClick;
        public     $OnAfterClick;
        public     $Name;

        function     Button()
        {
              $this->Name = 'MyButton';   
        }
       
        public function     Click()
        {
              $this->DoBeforeClick();
         
          echo     'Click!';
         
              $this->DoAfterClick();
        }

        private function     DoBeforeClick()
        {
          if (isset(    $this->OnBeforeClick))
          {
                $Event = $this->OnBeforeClick;
                $Event($this);
          }
        }

        private function     DoAfterClick()
        {
          if (isset(    $this->OnAfterClick))
          {
                $Event = $this->OnAfterClick;
                $Event($this);
          }
        }
      }
     
          //eclipse may warn here about syntax error but no problem, it runs well.
          $BeforeClickEventHandler = function($Sender) { echo $Sender->Name . ' (Before Click)'; }; 
          $AfterClickEventHandler = function($Sender) { echo $Sender->Name . ' (After Click)'; }; 
     
          $MyWidget = new Button();
          $MyWidget->OnBeforeClick = $BeforeClickEventHandler;
          $MyWidget->OnAfterClick = $AfterClickEventHandler;
          $MyWidget->Click();

    ?>

    output:
    MyButton (Before Click)
    Click!
    MyButton (After Click)

    i hope you find this useful.
    regards.
    emre
    ljackson at jjcons dot com
    6 years ago
    appears kwilson at shuttlebox dot net that you may have just made unintended side effect. Note that adding the global $variable to your test function make the closure function echo second rather than first So the anonymous function works as expected with respect to globals.

    <?php
        $variable     = "first";

            $closure = function() {
            global     $variable;

            echo     $variable . "\n";
        };

            $closure();

        function     test($closure)
        {
            global     $variable; //Note the scope added here
                $variable = "second";

                $closure();
        }

            test($closure);
    ?>

    prints:
    first
    second

    tested with php 5.3.1
    kwilson at shuttlebox dot net
    6 years ago
    Using the global keyword apparently pulls variables from the scope where the function was created, not where it is executed.

    Example:

    <?php
        $variable     = "first";
       
            $closure = function() {
            global     $variable;
           
            echo     $variable . "\n";
        };
       
            $closure();
       
        function     test($closure)
        {
                $variable = "second";
           
                $closure();
        }
       
            test($closure);
    ?>

    Will print:

    first
    first
    Suman Madavapeddi.
    5 years ago
    These  Closures are really interesting to me .This would be helpful.
    <?php
    Class Operations{
        public function     ops($x,$y,$op){
            switch (    $op){
                case     'ADD':return function() use($x,$y){
                                return     $x+$y."<br>";                           
                           };
                           break;
                case     'SUB': return function() use ($x,$y){
                                return     $x-$y."<br>";                           
                            };
                            break;
                default:    return function(){
                                return     "Operation is not supported by class"."<br>";
                            };
            }           
        }
    }

    $op =  new Operations();
    $fn1 = $op->ops(6,7,'ADD');
    echo     $fn1();

    $fn2 = $op->ops(6,2,'SUB');
    echo     $fn2();

    $fn2 = $op->ops(6,7,'MUL');
    echo     $fn2();
    ?>
    nbjayme at yahoo dot com
    2 years ago
    as of PHP version 5.3

    self::mycollection is an anonymous function array

    self::mycollection["funcId"]();   // error unknown

    To fix:

    $theFunc = & self::mycollection["funcId"];
    $theFunc();
    kukoman at pobox dot sk
    6 years ago
    be aware of  Fatal error: Using $this when not in object context when using in closures

    http://wiki.php.net/rfc/closures/removal-of-this
    Anonymous
    5 years ago
    use() parameters are early binding - they use the variable's value at the point where the lambda function is declared, rather than the point where the lambda function is called (late binding).

    If you want late binding put & before the variable inside use()
    <?php
    $fn     = function () use (&$var) { echo $var; };
    ?>
    Examples:
    <?php
    // problem 1: this should echo "Canada", not a php notice
    $fn = function () use ($country) { echo $country . "\n"; };
    $country = 'Canada';
    $fn();

    // problem 2: this should echo "Canada", not "UnitedStates"
    $country = 'UnitedStates';
    $fn = function () use ($country) { echo $country . "\n"; };
    $country = 'Canada';
    $fn();

    // problem 3: this should echo "Canada", not "UnitedStates"
    $country = (object)array('name' => 'UnitedStates');
    $fn = function () use ($country) { echo $country->name . "\n"; };
    $country = (object)array('name' => 'Canada');
    $fn();

    // problem 4: this outputs "Canada". if this outputs "Canada",
    // then so should problem 2 above. otherwise this should be
    // just as broken as problem 2 and be outputting "UnitedStates"
    $country = (object)array('name' => 'UnitedStates');
    $fn = function () use ($country) { echo $country->name . "\n"; };
    $country->name = 'Canada';
    $fn();
    ?>
    see http://bugs.php.net/bug.php?id=50980
    (I've just quoted from there, but if you want you can read there the whole feature request)
    Hayley Watson
    6 years ago
    In the code

    <?php
    function new_counter()
    {
            $counter = mt_rand();
        return function()use(&    $counter)
        {
            return ++    $counter;
        };
    }

    $t1 = new_counter();
    $t2 = new_counter();

    echo     $t1(),"\n";
    echo     $t1(),"\n";
    echo     $t2(),"\n";
    echo     $t2(),"\n";
    echo     $t1(),"\n";
    echo     $t1(),"\n";
    ?>

    The variable $counter is local to new_counter() and is used by reference by the returned lambda function.

    Because $counter is not static, a new variable is created each time new_counter() is called.

    But because the lambda function uses a REFERENCE to the $counter variable - and not a new local variable with a copy of the value $counter had when the lambda function was constructed - the $counter variable created when new_counter() ran still exists (because a reference to it still exists).

    Every lambda function has a variable reference "hardwired" into it. That variable therefore persists across calls to the lambda function - rather like a static variable.

    But that variable is only LOCAL to the new_counter() function that created it. As soon as new_counter() returns, it gives up its reference to $counter. When new_counter() is called again, it gets allocated a NEW $counter variable and gives a reference to THAT variable to the lambda function it constructs.

    So the lambda functions in $t1 and $t2 each have their OWN $counter variable - separate from the other's, which persists from one call to the next.

    The effect is very similar to declaring and initialising $counter as static within the lambda function - and then it doesn't need to use anything from new_counter() - but you can't initialise a static variable with a function call like mt_rand()!

    Pending a decision on what it should mean, $this is not currently (as of 5.3.2) usable within anonymous functions.

    There are roughly two positions (plus attempts at compromise), that can be called "early" and "late".

    Early: $this refers to the object in whose scope the anonymous function is constructed.
    <?php
    class Creator
    {
       public function     make_anonymous()
       {
           return function()
           {
               return     $this;
           };
       }
    }

    class     Caller
    {
       public     $p;
       public function     call_anonymous($f)
       {
               $this->p = $f();
       }
    }

    $alpha = new Creator;
    $omega = new Caller;
    $omega->call_anonymous($alpha->create_anonymous());
    // $omega->p === $alpha
    ?>

    Late: $this refers to the object in whose scope the anonymous function is called.

    <?php
    class Creator
    {
       public function     make_anonymous()
       {
           return function()
           {
               return     $this;
           };
       }
    }

    class     Caller
    {
       public     $p;
       public function     call_anonymous($f)
       {
               $this->p = $f();
       }
    }

    $alpha = new Creator;
    $omega = new Caller;
    $omega->call_anonymous($alpha->create_anonymous());
    // $omega->p === $omega
    ?>

    So until this is cleared up, $this won't work in an anonymous function. (Personally, I favour the early method; otherwise the anonymous function - and therefore its Creator - has access to all of the Caller's private properties.)
    nathan at crause dot name
    2 years ago
    One item not mentioned anywhere is how to invoke an anonymous function "in-line".

    To explain what I mean, let me use an actual example. Instead of creating code like this:
    <?php
    $wording     = ($from == 0 && $to == 0
            ? '< 1 Year'
            : ($to == 9999
                ? ($from - 1) . '+ Years'
                : "$from - $to Years"));
    ?>

    You might, instead, want to use an anonymous function right in the assignment line. However, doing:
    <?php
    $wording     = function() use ($from, $to) { ... }
    ?>
    would actually assign $wording to the Closure instance, not actually execute the function.

    The best way to do this that I've found is:
    <?php
    $wording     = call_user_func(function() use ($from, $to) {
        if (    $from == 0 && $to == 0) return '< 1 Year';
        if (    $to == 9999) return ($from - 1) . '+ Years';

        return     "$from - $to Years";
    });
    ?>

    It's a little longer than the first code sample, but I think it's more readable, and using this methodology opens up the ability to use more complex means of calculating a value without filling the variable scope with a bunch of temporary variables.
    dave at mausner dot us
    6 years ago
    Ulderico had it almost right.  To avoid confusing the interpreter, when using a simple closure stored in a $variable, you must invoke the nameless function using the function syntax.

    <?php
    $helloworld     = function(){
        return     "each hello world is different... ".date("His");
    };

    echo     $helloworld( );
    ?>

    Note the empty actual-parameter list in the "echo".  NOW IT WORKS.
    To Top