[php] First letter after backslash is treated like an escape sequence in single quoted strings

[Sobak]

I think that snippet makes it obvious

Snippet with error: #571a31319d764
Language: php Kadet\Highlighter\Language\Php
Version: 0.8.0-1e4513b

[kadet1090]

It's correct behavior for double quoted strings, where every character after \ is treated like escape sequence (\n, \r etc.), in single quoted strings only \ and ' are valid escapes, i'll try to somehow separate them.