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<?php $strings = [ "(a+b)", "(a+b)(ab+ba)", "(a+b)(ab+ba)(ab+ba)", "(ab+ba)", "a+b", " (a+b)(, (a+b)a" ]; $pattern = '/^\(a\+b\)(?:\(ab\+ba\))*$/'; foreach ($strings as $string) { preg_match($pattern, $string, $matches); print_r($matches); }
Output for 7.1.0 - 7.1.25, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
Array ( [0] => (a+b) ) Array ( [0] => (a+b)(ab+ba) ) Array ( [0] => (a+b)(ab+ba)(ab+ba) ) Array ( ) Array ( ) Array ( )
preferences:
109.23 ms | 1468 KiB | 4 Q