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<?php $string = '--'; $doesNotMatchInPhp7 = '/(?|(---)|(-))\1$/'; $matchesInPhp7 = '/(?|(-)|(---))\1$/'; var_dump(preg_match($doesNotMatchInPhp7, $string)); var_dump(preg_last_error()); var_dump(preg_match($matchesInPhp7, $string));
Output for 5.6.38 - 5.6.40, 7.3.0 - 7.3.32, 7.4.0 - 7.4.25, 8.0.0 - 8.0.12, 8.1rc1 - rc3
int(1) int(0) int(1)
Output for 7.0.0 - 7.0.33, 7.1.0 - 7.1.27, 7.2.0 - 7.2.33
int(0) int(0) int(1)

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49.43 ms | 461 KiB | 5 Q