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run code in 200+ php & hhvm versions
Bugs & Features
<?php $a = 'рв 2134 хт'; echo preg_replace('\s', '', mb_strtoupper($a));
Output for 4.3.11 - 7.2.0
Warning: preg_replace(): Delimiter must not be alphanumeric or backslash in /in/aYtfS on line 4
Output for 4.3.0 - 4.3.10
Warning: Delimiter must not be alphanumeric or backslash in /in/aYtfS on line 4