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<?php echo "Normal match:\n"; preg_match('/two/', 'two', $match); var_dump($match); echo "Unmatched $1 is not reported:\n"; preg_match('/(one)?two/', 'two', $match); var_dump($match); preg_match('/two(three)?/', 'two', $match); var_dump($match); echo "Unmatched $1 is reported if $2 is set:\n"; preg_match('/(one)?(two)/', 'two', $match); var_dump($match); echo "Unmatched $2 is not reported even though $1 is set:\n"; preg_match('/(two)(three)?/', 'two', $match); var_dump($match);
Output for 7.3.0 - 7.3.33, 7.4.0 - 7.4.29, 8.0.0 - 8.0.19, 8.1.0 - 8.1.6
Normal match: array(1) { [0]=> string(3) "two" } Unmatched $1 is not reported: array(1) { [0]=> string(3) "two" } array(1) { [0]=> string(3) "two" } Unmatched $1 is reported if $2 is set: array(3) { [0]=> string(3) "two" [1]=> string(0) "" [2]=> string(3) "two" } Unmatched $2 is not reported even though $1 is set: array(2) { [0]=> string(3) "two" [1]=> string(3) "two" }

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