PHP Closure by Reference

closure.php

// Set counter  
$i = 0;  
// Increase counter within the scope  
// of the function  
$closure = function () use ($i){ $i++; };  
// Run the function  
$closure();  
// The global count hasn’t changed  
echo $i; // Returns 0

// Reset count  
$i = 0;  
// Increase counter within the scope  
// of the function but pass it as a reference  
$closure = function () use (&$i){ $i++; };  
// Run the function  
$closure();  
// The global count has increased  
echo $i; // Returns 1