Rule Definition
Most of the times the functions only need to use the values from their parameters without changing them. In such cases, you can safely pass those parameters by reference (e.g., function(&$parameter) rather than value (e.g function($parameter)) and avoid having to make memory-intensive copies and therefore increase the performance of the application.

Remediation
try and passe the parameters by reference when these parameters are only used in read mode.

Violation Code Sample

<?php

function($parameter) 
{
$test = $parameter
}
?>

Fixed Code Sample

<?php

function(&$parameter) 
{
$test = $parameter
}
?>