I know $a =& $b assigns $a as a reference to $b and I already read some answers about it, but no one provides a real useful example usage includes: What do the "=&" and "&=" operators in PHP mean?
Could any one provide a minimal example to show how =& could be useful in PHP? Why might somebody want to have two names for a single variable?
Here's a very simple example. You are assigning the reference of $var1 to $var2 , so when you change $var2 , $var1 value changes.
<?php $var1 = 10; $var2 = 20; $var2 = &$var1; $var2 = 200; echo $var1; // 200; 
Suppose some user defined function manipulate a string:
function test($string){ $string.='bar'; return $string; } In this case, you would have to attribute the return of the function back to the variable:
$foo='foo'; $foo=test($foo); Passing the variable by reference you could eliminate some code:
function test(&$string){ $string.='bar'; } $foo='foo'; test($foo); Just like, for example, the native settype works. Look the ampersand at the manual.
Really useful example is modifying tree-alike structures:
Assuming you have a tree path like 'a.b.c' and an array:
array( 'a' => array( 'b' => array( 'c' => array(), ), ), ) and you need to insert a new value in the deepest element. That you could end up with something like (not tested, just for demonstration purposes):
$parts = explode('.', $path); $node = &$tree; foreach ($parts as $part) { if (isset($node[$part])) { $node = &$node[$part]; } else { $node = null; break; } } if (!is_null($node)) { $node[] = 'new value'; } 
$tree was initialized?