PHP 7.0.6 Released

    INSTANCEOF

    PHP code

    <?php
    /*
     * 
     * opcode number: 138
     */
    $obj = new A();

    if (    $obj instanceof A) {
       echo     'A';
    }
    ?>

    PHP opcodes

    Function name: (null)

    Compiled variables: !0=$obj

    line#op fetchextreturn operands
    60 ZEND_FETCH_CLASS   :0 'A'
     1 NEW   $1 :0
     2 DO_FCALL_BY_NAME  0   
     3 ASSIGN     !0,$1
    84 ZEND_FETCH_CLASS   :4 'A'
     5 ZEND_INSTANCEOF   ~5 !0,$4
     6 JMPZ     ~5,->9
    97 ECHO     'A'
    108 JMP     ->9
    119 RETURN     1

    User Contributed Notes

    cody at codysnider dot com
    3 years ago
    When checking instanceof against a subclass of the class in question, it will return true.

    <?php

    class Foo {

        public     $foobar = 'Foo';
       
        public function     test() {
            echo     $this->foobar . "\n";
        }

    }

    class     Bar extends Foo {

        public     $foobar = 'Bar';

    }

    $a = new Foo();
    $b = new Bar();

    echo     "use of test() method\n";
    $a->test();
    $b->test();

    echo     "instanceof Foo\n";
    var_dump($a instanceof Foo); // TRUE
    var_dump($b instanceof Foo); // TRUE

    echo "instanceof Bar\n";
    var_dump($a instanceof Bar); // FALSE
    var_dump($b instanceof Bar); // TRUE

    echo "subclass of Foo\n";
    var_dump(is_subclass_of($a, 'Foo')); // FALSE
    var_dump(is_subclass_of($b, 'Foo')); // TRUE

    echo "subclass of Bar\n";
    var_dump(is_subclass_of($a, 'Bar')); // FALSE
    var_dump(is_subclass_of($b, 'Bar')); // FALSE

    ?>

    Result (CLI, 5.4.4):

    use of test() method
    Foo
    Bar
    instanceof Foo
    bool(true)
    bool(true)
    instanceof Bar
    bool(false)
    bool(true)
    subclass of Foo
    bool(false)
    bool(true)
    subclass of Bar
    bool(false)
    bool(false)
    krall dot eugene at gmail dot com
    1 year ago
    When checking instanceof against a class that implements the class in question, it will return true.

    <?php

    interface ExampleInterface
    {
        public function     interfaceMethod();

    }

    class     ExampleClass implements ExampleInterface
    {
        public function     interfaceMethod()
        {
            return     'Hello World!';
        }
    }

    $exampleInstance = new ExampleClass();

    if(    $exampleInstance instanceof ExampleInterface)
        echo     'Yes, it is';
    else
        echo     'No, it is not';

    ?>

    The result:

    Yes, it is
    portugal {at} jawira {dot} com
    10 months ago
    I'm commenting here because the note from "admin at torntech" is incomplete. You can perfectly replace "is_a()" function with "instanceof" operator. However you must use a variable to store the class name, otherwise you will get a Parse error:

    <?php
    $object     = new \stdClass();
    $class_name = '\stdClass';

    var_dump($object instanceof $class_name);    // bool(true)
    var_dump($object instanceof '\stdClass');    // Parse error: syntax error, unexpected ''\stdClass'' (T_CONSTANT_ENCAPSED_STRING)
    ?>

    Please go to Type Operators page for more details about "instanceof": http://php.net/manual/en/language.operators.type.php
    asdf at asdf dot com
    4 years ago
    Please note, that you get no warnings on non-existent classes:

    <?php
    class A() {
    }

    $a = new A();

    $exists = ($a instanceof A); //TRUE
    $exists = ($a instanceof NonExistentClass); //FALSE
    admin at torntech dot com
    1 year ago
    Despite this section being opcode examples, for php 5.3+ see also is_a()
    *Note php 5.0 - 5.2 is_a() was depreciated in favor of instanceof but was undepreciated in 5.3+.

    Allows for string comparison against the class name and functions in the same manner as cody mentions like so.
    <?php
    namespace Foo{
        class     Bar {}
        class     Baz extends Bar{}
    }
    namespace {
            $baz = new Foo\Baz;

            var_dump($baz instanceof Foo\Bar);
            /* returns bool(true) */

            var_dump(is_a($baz, 'Foo\\Bar'));
            /* returns bool(true) */

            var_dump($baz instanceof 'Foo\\Bar');
            /* returns Runtime parse error */
    }
    ?>
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