Question

Can anyone tell me what is happening here?

<?php
// true
var_dump('\\ ' === '\ ');

// false
var_dump('\\\\ ' === '\\ ');

// true
var_dump('\\\\ ' === '\\\ ');

Answer 1

\ inside a string literal introduces several types of escape sequences, \\ is the escape sequence for a literal “\”. But, \s that don’t resolve to an escape sequence are also taken as literal “\”.

Therefor, '\\ ' stands for the string “\ “, '\\\\ ' stands for the string “\\ “, just as '\\\ '. Try:

echo '\\\\ ';   -> \\ 

See http://php.net/manual/en/language.types.string.php#language.types.string.syntax.single.