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Reference assignment operator in php =&
$var2 = $var1; $var2 = &$var1; Example:
$GLOBALS['a']=1; function test() { global $a; $local=2; $a=&$local; } test(); echo $a; Why is $a still 1 ?
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3 Answers
The operator =& works with references and not values. The difference between $var2=$var1 and $var2=&$var1 is visible in this case :
$var1 = 1; $var2 = $var1; $var1 = 2; echo $var1 . " " . $var2; // Prints '2 1' $var1 = 1; $var2 =& $var1; $var1 = 2; echo $var1 . " " . $var2; // Prints '2 2' When you use the =& operator you don't say to $var2 "take the value of $var1 now" instead you say something like "Your value will be stored at the exact same place that the value of $var1". So anytime you change the content of $var1 or $var2, you will see the modification in the two variables.
For more informations look on PHP.net
EDIT : For the global part, you'll need to use $GLOBALS["a"] =& $local; Cf. documentation.
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Colin Hebert
"If you assign a reference to a variable declared global inside a function, the reference will be visible only inside the function. You can avoid this by using the $GLOBALS array." Check the link i gave you, there is an entire section about globals.
When you do $var2 = $var1, PHP creates a copy of $var1, and places it in $var2. However, if you do $var2 = &$var1, no copy is made. Instead, PHP makes $var2 point at $var1 - what this means is that you end up with two variables that point at the exact same thing.
An example:
$var1 = "Foo"; $var2 = $var1; // NORMAL assignment - $var1's value is copied into $var2 $var3 = &$var1; // NOT normal copy! echo $var2; // Prints "Foo". echo $var3; // Also prints "Foo". $var1 = "Bar"; // Change $var1. echo $var2; // Prints "Foo" as before. echo $var3; // Now prints "Bar"! 
global $a; This is equivalent to:
$a = &$GLOBALS['a']; When you assign $a a new reference, you're changing $a and not $GLOBALS['a'].
What do you expect to be output below?
$GLOBALS['a']=1; function test() { $a='foobar'; // $a is a normal variable $a=&$GLOBALS['a']; // same as: global $a; $local=2; $a=&$local; } test(); echo $a; 