It bit me today, so putting it here in the hope it will help others:
If you call array_key_exists() on an object of a class that implements ArrayAccess, ArrayAccess::offsetExists() wil NOT be called.
(PHP 5 >= 5.0.0, PHP 7)
Interface to provide accessing objects as arrays.
Example #1 Basic usage
<?php
class obj implements ArrayAccess {
private $container = array();
public function __construct() {
$this->container = array(
"one" => 1,
"two" => 2,
"three" => 3,
);
}
public function offsetSet($offset, $value) {
if (is_null($offset)) {
$this->container[] = $value;
} else {
$this->container[$offset] = $value;
}
}
public function offsetExists($offset) {
return isset($this->container[$offset]);
}
public function offsetUnset($offset) {
unset($this->container[$offset]);
}
public function offsetGet($offset) {
return isset($this->container[$offset]) ? $this->container[$offset] : null;
}
}
$obj = new obj;
var_dump(isset($obj["two"]));
var_dump($obj["two"]);
unset($obj["two"]);
var_dump(isset($obj["two"]));
$obj["two"] = "A value";
var_dump($obj["two"]);
$obj[] = 'Append 1';
$obj[] = 'Append 2';
$obj[] = 'Append 3';
print_r($obj);
?>
The above example will output something similar to:
bool(true)
int(2)
bool(false)
string(7) "A value"
obj Object
(
[container:obj:private] => Array
(
[one] => 1
[three] => 3
[two] => A value
[0] => Append 1
[1] => Append 2
[2] => Append 3
)
)
It bit me today, so putting it here in the hope it will help others:
If you call array_key_exists() on an object of a class that implements ArrayAccess, ArrayAccess::offsetExists() wil NOT be called.
<?php
/**
* ArrayAndObjectAccess
* Yes you can access class as array and the same time as object
*
* @author Yousef Ismaeil <cliprz@gmail.com>
*/
class ArrayAndObjectAccess implements ArrayAccess {
/**
* Data
*
* @var array
* @access private
*/
private $data = [];
/**
* Get a data by key
*
* @param string The key data to retrieve
* @access public
*/
public function &__get ($key) {
return $this->data[$key];
}
/**
* Assigns a value to the specified data
*
* @param string The data key to assign the value to
* @param mixed The value to set
* @access public
*/
public function __set($key,$value) {
$this->data[$key] = $value;
}
/**
* Whether or not an data exists by key
*
* @param string An data key to check for
* @access public
* @return boolean
* @abstracting ArrayAccess
*/
public function __isset ($key) {
return isset($this->data[$key]);
}
/**
* Unsets an data by key
*
* @param string The key to unset
* @access public
*/
public function __unset($key) {
unset($this->data[$key]);
}
/**
* Assigns a value to the specified offset
*
* @param string The offset to assign the value to
* @param mixed The value to set
* @access public
* @abstracting ArrayAccess
*/
public function offsetSet($offset,$value) {
if (is_null($offset)) {
$this->data[] = $value;
} else {
$this->data[$offset] = $value;
}
}
/**
* Whether or not an offset exists
*
* @param string An offset to check for
* @access public
* @return boolean
* @abstracting ArrayAccess
*/
public function offsetExists($offset) {
return isset($this->data[$offset]);
}
/**
* Unsets an offset
*
* @param string The offset to unset
* @access public
* @abstracting ArrayAccess
*/
public function offsetUnset($offset) {
if ($this->offsetExists($offset)) {
unset($this->data[$offset]);
}
}
/**
* Returns the value at specified offset
*
* @param string The offset to retrieve
* @access public
* @return mixed
* @abstracting ArrayAccess
*/
public function offsetGet($offset) {
return $this->offsetExists($offset) ? $this->data[$offset] : null;
}
}
?>
Usage
<?php
$foo = new ArrayAndObjectAccess();
// Set data as array and object
$foo->fname = 'Yousef';
$foo->lname = 'Ismaeil';
// Call as object
echo 'fname as object '.$foo->fname."\n";
// Call as array
echo 'lname as array '.$foo['lname']."\n";
// Reset as array
$foo['fname'] = 'Cliprz';
echo $foo['fname']."\n";
/** Outputs
fname as object Yousef
lname as array Ismaeil
Cliprz
*/
?>
The indexes used in an ArrayAccess object are not limited to strings and integers as they are for arrays: you can use any type for the index as long as you write your implementation to handle them. This fact is exploited by the SplObjectStorage class.
Conclusion: Type hints \ArrayAccess and array are not compatible.
<?php
class MyArrayAccess implements \ArrayAccess
{
public function offsetExists($offset)
{
}
public function offsetSet($offset, $value)
{
}
public function offsetGet($offset)
{
}
public function offsetUnset($offset)
{
}
}
function test(array $arr)
{
}
function test2(\ArrayAccess $arr)
{
}
$arrObj = new MyArrayAccess();
test([]); //result: works!
test($arrObj); //result: does NOT work
test2([]); //result: does NOT work
test2($arrObj); // result: works!
?>
Objects implementing ArrayAccess may return objects by references in PHP 5.3.0.
You can implement your ArrayAccess object like this:
class Reflectable implements ArrayAccess {
public function set($name, $value) {
$this->{$name} = $value;
}
public function &get($name) {
return $this->{$name};
}
public function offsetGet($offset) {
return $this->get($offset);
}
public function offsetSet($offset, $value) {
$this->set($offset, $value);
}
...
}
This base class allows you to get / set your object properties using the [] operator just like in Javascript:
class Boo extends Reflectable {
public $name;
}
$obj = new Boo();
$obj['name'] = "boo";
echo $obj['name']; // prints boo
Sadly you cannot assign by reference with the ArrayAccess (at least in PHP 5.3.23)
It's too bad there is no syntax for optionally passing variables by reference to functions (a feature in retro PHP).
That option would have let ArrayAccess fully mimic the functionality of normal array assignments:
<?php
$var = 'hello';
$arr = array();
$arr[0] = $var;
$arr[1] = &$var;
$var = 'world';
var_dump($arr[0], $arr[1]);
// string(5) "hello"
// string(5) "world"
?>
Declaring "function offsetSet($offset, &$value)" will cause a fatal error.
So to assign by ref you can use an ugly function call, for example:
<?php
class obj implements ArrayAccess {
// ... ArrayAccess example code ...
public function &offsetSetRef($offset, &$value) {
if (is_null($offset)) {
$this->container[] = &$value;
} else {
$this->container[$offset] = &$value;
}
return $value; // should return in case called within an assignment chain
}
}
$var = 'hello';
$obj = new obj();
$obj[0] = $var;
//$obj[1] = &$var; // Fatal error: Cannot assign by reference to overloaded object
$obj->offsetSetRef(1, $var); // the work around
$var = 'world';
var_dump($obj[0], $obj[1]);
// string(5) "hello"
// string(5) "world"
?>
reset() method may not work as you expect with ArrayAccess objects.
Using reset($myArrayAccessObject) returns the first property from $myArrayAccessObject, not the first item in the items array.
If you want to use the reset() method to return the first array item, then you can use the following simple workaround:
<?php
class MyArrayAccessObject implements Iterator, ArrayAccess, Countable {
protected $first = null; //WARNING! Keep this always first.
protected $items = null;
private function supportReset() {
$this->first = reset($this->items); //Support reset().
}
// ...
public function offsetSet($offset, $value) {
if ($offset === null) {
$this->items[] = $value;
}
else {
$this->items[$offset] = $value;
}
$this->supportReset();
}
}
?>
Finally, call $this->supportReset() in the end of all methods that change the internal $items array, such as in offsetSet(), offsetUnset() etc.
This way, you can use the reset() method as normally:
<?php
$firstArrayItem = reset($myArrayAccessObject);
?>
A class that implements ArrayAccess will not work with array_push
For example:
<?php
class TestArrayAccess implements ArrayAccess {
private $container = array();
// ArrayAccess methods
}
$obj = new TestArrayAccess();
array_push($obj, 'Hello World!'); // Nothing will be added
?>
One way of being able to use array_push would be by adding a toArray() method (note the return value is a reference).
<?php
class TestArrayAccess implements ArrayAccess {
private $container = array();
// ArrayAccess methods
public function &toArray() {
return $this->container;
}
}
$obj = new TestArrayAccess();
array_push($obj->toArray(), 'Hello World!'); // Will now be added to array
?>
Objects implementing ArrayAccess do not support the increment/decrement operators ++ and --, unlike array() and ArrayObject()
<?php
class MyArray implements ArrayAccess
{
// offsetSet, offsetGet etc implemented
}
$x = new MyArray() ;
$x[0] = 0 ;
$x[0]++ ; //error 'Indirect modification of overloaded element has no effect'
$x[0] += 1 ; // this works OK.
?>