3v4l.org

run code in 200+ php & hhvm versions
<?php preg_match_all('~[\\\\a-z0-9_]~', 'a\\\\b', $matches); print_r($matches); preg_match_all('~[a-z0-9_\\\\]~', 'a\\\\b', $matches); print_r($matches); preg_match_all('~[\\d-z]~', 'a\\\\b', $matches); print_r($matches); preg_match_all('~[\\\\d-z]~', 'a\\\\b', $matches); print_r($matches);
based on QuZv8
Output for 7.3.0 - 7.4.0alpha1
Array ( [0] => Array ( [0] => a [1] => \ [2] => \ [3] => b ) ) Array ( [0] => Array ( [0] => a [1] => \ [2] => \ [3] => b ) ) Warning: preg_match_all(): Compilation failed: invalid range in character class at offset 3 in /in/hBE88 on line 8 Array ( [0] => Array ( [0] => a [1] => \ [2] => \ [3] => b ) ) Array ( [0] => Array ( [0] => \ [1] => \ ) )
Output for 7.1.25 - 7.2.19
Array ( [0] => Array ( [0] => a [1] => \ [2] => \ [3] => b ) ) Array ( [0] => Array ( [0] => a [1] => \ [2] => \ [3] => b ) ) Array ( [0] => Array ( ) ) Array ( [0] => Array ( [0] => \ [1] => \ ) )