How does the “&” operator work in a PHP function?

Question

Please see this code:

function addCounter(&$userInfoArray) {
    $userInfoArray[\'counter\']++;
    return $userInfoArray[\'counter\'];
}

$userInfoArray         


        

Answer 1

The & operator tells PHP not to copy the array when passing it to the function. Instead, a reference to the array is passed into the function, thus the function modifies the original array instead of a copy.

Just look at this minimal example:

Here, the output is:

1
2

– the call to foo didn’t modify $x. The call to bar, on the other hand, did.