Understanding Ampersand Before PHP Function Names – Returning By Reference

ampersand-before-php-function-names.php

<?php
// You may have wondered how a PHP function defined as below behaves:
function &config_byref()
{
    static $var = "hello";

    return $var;
}
// the value we get is "hello"
$byref_initial = config_byref();

// let's change the value
$byref_initial = "world";

// Let's get the value again and see
echo "Byref, new value: " . config_byref() . "\n"; // We still get "hello"

// However, let’s make a small change:
// We’ve added an ampersand to the function call as well. In this case, the function returns "world", which is the new value.
// the value we get is "hello"
$byref_initial = &config_byref();

// let's change the value
$byref_initial = "world";

// Let's get the value again and see
echo "Byref, new value: " . config_byref() . "\n"; // We now get "world"

// If you define the function without the ampersand, like follows:

// function config_byref()
// {
//     static $var = "hello";

//     return $var;
// }

// Then both the test cases that we had previously would return "hello", regardless of whether you put ampersand in the function call or not.