PHP variables reference and memory usage

Question

According to php manual:

// Note:
// $a and $b are completely equal here. $a is not pointing to $b or vice versa.
// $a and $b          


        

Answer 1

PHP does not duplicate on assignment, but on write. See Copy-on-Write in the PHP Language (Jan 18 2009; by Akihiko Tozawa, Michiaki Tatsubori, Tamiya Onodera and Yasuhiko Minamide; PDF file) for a scientific discussion of it, Do not use PHP references (Jan 10, 2010; by Jan Schlüter) for some fun and my own take is References to the Max with more references.

Answer 2

PHP uses copy-on-write so it won't use more memory for the duplicated strings until you modify them.