Returning References

Returning by-reference is useful when you want to use a function to find which variable a reference should be bound to. When returning references, use this syntax:


<?php

function &find_var($param)

{

    /* ...code... */

    return $found_var;

}



$foo =& find_var($bar);

$foo->x = 2;

?>

In this example, the property of the object returned by the find_var 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 return by-reference, not a copy as usual, and to indicate that reference binding, rather than usual assignment, should be done for $foo. & by function definition is optional in class methods.

User Contributed Notes
Returning References

obscvresovl at NOSPAM dot hotmail dot com
24-Dec-2004 03:09


An example of returning references:



<?



$var = 1;

$num = NULL;



function &blah()

{

    $var =& $GLOBALS["var"]; # the same as global $var;

    $var++;

    return $var;

}



$num = &blah();



echo $num; # 2



blah();



echo $num; # 3



?>



Note: if you take the & off from the function, the second echo will be 2, because without & the var $num contains its returning value and not its returning reference.

hawcue at yahoo dot com
16-Mar-2004 09:58


Be careful when using tinary operation condition?value1:value2



See the following code:



$a=1;

function &foo()

{

  global $a;

  return isset($a)?$a:null;

}

$b=&foo();

echo $b;   // shows 1

$b=2;

echo $a;   // shows 1 (not 2! because $b got a copy of $a)



To let $b be a reference to $a, use "if..then.." in the function.

contact at infopol dot fr
12-Feb-2004 11:36


A note about returning references embedded in non-reference arrays :



<?

$foo;



function bar () {

    global $foo;

    $return = array();

    $return[] =& $foo;

    return $return;

}



$foo = 1;

$foobar = bar();

$foobar[0] = 2;

echo $foo;

?>



results in "2" because the reference is copied (pretty neat).

zayfod at yahoo dot com
03-Dec-2003 11:23


There is a small exception to the note on this page of the documentation. You do not have to use & to indicate that reference binding should be done when you assign to a value passed by reference the result of a function which returns by reference.



Consider the following two exaples:



<?php



function    & func_b ()

{

    $some_var = 2;

    return $some_var;

}



function    func_a (& $param)

{

    # $param is 1 here

    $param = & func_b();

    # $param is 2 here

}



$var = 1;

func_a($var);

# $var is still 1 here!!!



?>



The second example works as intended:



<?php



function    & func_b ()

{

    $some_var = 2;

    return $some_var;

}



function    func_a (& $param)

{

    # $param is 1 here

    $param = func_b();

    # $param is 2 here

}



$var = 1;

func_a($var);

# $var is 2 here as intended



?>



(Experienced with PHP 4.3.0)

i at tc dot se
08-Oct-2003 08:54


In the following example, if $key does not exist in the "private" $arr when calling get_value_for($key), then $this->arr[$key] will be set, which is not the intended action.



class silly_array {

    var $arr;

    ...

    function & get_value_for($key) {

        return $this->arr[$key];

    }

    ...

}



Therefore, one should check if $key exists in the array first, before returning its value. Something like this:



function & get_value_for($key) {

    return isset($this->arr[$key]) ? $this->arr[$key] : false;

}