Online PHP editor | refs for HREEu

<?php $strings = [ 'asds asds asdas dasds', 'asdasd asds asd key1:asds', 'asdasd asdsd key2:asdsd asd key1: asdsad', 'asddfs asfasas key2: asds asd key2', // invalid 'asds key3:sdsd asdsad key1:', // invalid 'asds asds asd key1:asdsd key2: assadas asfsaf', 'asdsd aaa:bbb asds', // invalid 'sds asdsad asdsd :asdsd', // invalid ]; foreach ($strings as $string) { var_export([ $string, preg_match( '/(?!key1|key2)\b\S+: ?\S+/', $string, $m ) ? "Invalid substring: {$m[0]}" : 'No invalid substring detected' ]); echo "\n---\n"; }