Strict Standards: Only variables should be assigned by reference PHP 5.4

This error message is indicating that a value is being assigned to a variable by reference, which is not allowed in PHP version 5.4 or later. In earlier versions of PHP, it was possible to assign a value to a variable by reference, but this is no longer allowed in more recent versions. To fix this error, you will need to remove the "&" symbol from any assignments where a value is being assigned to a variable by reference.