This sniff is broken for \e, \1 (etc.), and for \u all of which are valid uses for double quotes.

Also, your composer.json states a minimum PHP of 5.1.2 and then defines \v and \f as allowed characters which is not the case until PHP 5.2.5. I'm not sure how one can test that sort of thing using your current testing framework.

An example:

---------------------------------------------------------------------- 33 | ERROR | [x] String "\e[0;32mPASS\e[0m" does not require | | double quotes; use single quotes instead ---------------------------------------------------------------------- 

and

---------------------------------------------------------------------- 3 | ERROR | [x] String "\1" does not require double quotes; use | | single quotes instead ---------------------------------------------------------------------- 

Btw., \e has been available since 5.4.4, and \u since 7.0.0.

Link to the manual: http://php.net/manual/en/language.types.string.php#language.types.string.syntax.double

Probably changing the $allowedChars array to this:

 $allowedChars = array( '\0', '\1', '\2', '\3', '\4', '\5', '\6', '\7', '\n', '\r', '\t', '\x', '\b', '\'', ); if (phpversion() >= '5.2.5') { $allowedChars[] = '\v'; $allowedChars[] = '\f'; } if (phpversion() >= '5.4.4') { $allowedChars[] = '\e'; } if (phpversion() >= '7.0.0') { $allowedChars[] = '\u'; }

is best, but then how you go about testing that on different platforms with the current test framework is as said, impossible.