When to pass-by-reference in PHP

Question

Im wondering if its good practice to pass-by-reference when you are only reading a variable, or if it should always be passed as a value.

Example with pass-by-refere

Answer 1

PHP makes use of copy-on-write as much as possible (whenever it would typically increase performance) so using references is not going to give you any performance benefit; it will only hurt. Use references only when you really need them. From the PHP Manual:

Do not use return-by-reference to increase performance. The engine will automatically optimize this on its own. Only return references when you have a valid technical reason to do so.