Php/docs/language.references.return
Returning References
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:
<?phpclass 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.
To use the returned reference, you must use reference assignment:
<?phpfunction &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:
<?phpfunction &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.
