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run code in 150+ php & hhvm versions
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<?php $string1 = "aaabchr"; $string2 = "qwntfschrprtkjs"; $regex = '/^(?:.(?!chr))*(?:[bcdfghjklmnpqrstvwxz](?!chr)){4}(?:.(?!chr))*$/i'; var_dump( preg_match($regex, $string1), preg_match($regex, $string2) );
Output for 4.3.0 - 5.6.28, hhvm-3.10.0 - 3.12.0, 7.0.0 - 7.1.0
int(0) int(0)