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run code in 200+ php & hhvm versions
Bugs & Features
<?php preg_match( '/^\[#(\d+)\]/', '[#12345] Subj6ect', $matches); echo $matches[1]; // 1234
based on obRDI
Output for 5.6.0 - 5.6.30, hhvm-3.12.14 - 3.17.3, 7.0.0 - 7.3.0beta1
12345