Returning References

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Returning by reference is useful when you want to use a function to find to which variable a reference should be bound. Do not use return-by-reference to increase performance. The engine will automatically optimize this on its own. Only return references when you have a valid technical reason to do so. To return references, use this syntax:


<?php
class foo {
    public $value = 42;

    public function &getValue() {
        return $this->value;
    }
}

$obj = new foo;
$myValue = &$obj->getValue(); // $myValue is a reference to $obj->value, which is 42.
$obj->value = 2;
echo $myValue;                // prints the new value of $obj->value, i.e. 2.
?>

In this example, the property of the object returned by the getValue function would be set, not the copy, as it would be without using reference syntax.

Note: Unlike parameter passing, here you have to use & in both places - to indicate that you want to return by reference, not a copy, and to indicate that reference binding, rather than usual assignment, should be done for $myValue.

Note: If you try to return a reference from a function with the syntax: return ($this->value); this will not work as you are attempting to return the result of an expression, and not a variable, by reference. You can only return variables by reference from a function - nothing else. Since PHP 5.1.0, an E_NOTICE error is issued if the code tries to return a dynamic expression or a result of the new operator.

To use the returned reference, you must use reference assignment:


<?php
function &collector() {
  static $collection = array();
  return $collection;
}
$collection = &collector();
$collection[] = 'foo';
?>

To pass the returned reference to another function expecting a reference you can use this syntax:


<?php
function &collector() {
  static $collection = array();
  return $collection;
}
array_push(collector(), 'foo');
?>

Note: Note that array_push(&collector(), 'foo'); will not work, it results in a fatal error.

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Document created the 30/01/2003, last modified the 26/10/2018
Source of the printed document:https://www.gaudry.be/en/php-rf-language.references.return.html

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References

Manuel PHP : http://php.net

These references and links indicate documents consulted during the writing of this page, or which may provide additional information, but the authors of these sources can not be held responsible for the content of this page.
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