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<?php $re = '%^ ((?=x))? ((?=y))? (\w) $%mx'; $str = 'x y z'; preg_match_all($re, $str, $matches, PREG_SET_ORDER | PREG_UNMATCHED_AS_NULL, 0); // Print the entire match result var_dump($matches);
Output for 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 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.4, 8.3.6
array(3) { [0]=> array(4) { [0]=> string(1) "x" [1]=> string(0) "" [2]=> NULL [3]=> string(1) "x" } [1]=> array(4) { [0]=> string(1) "y" [1]=> NULL [2]=> string(0) "" [3]=> string(1) "y" } [2]=> array(4) { [0]=> string(1) "z" [1]=> NULL [2]=> NULL [3]=> string(1) "z" } }
Output for 8.3.5
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0 array(3) { [0]=> array(4) { [0]=> string(1) "x" [1]=> string(0) "" [2]=> NULL [3]=> string(1) "x" } [1]=> array(4) { [0]=> string(1) "y" [1]=> NULL [2]=> string(0) "" [3]=> string(1) "y" } [2]=> array(4) { [0]=> string(1) "z" [1]=> NULL [2]=> NULL [3]=> string(1) "z" } }
Output for 7.1.0 - 7.1.33
Notice: Use of undefined constant PREG_UNMATCHED_AS_NULL - assumed 'PREG_UNMATCHED_AS_NULL' in /in/bu1Sf on line 13 Warning: A non-numeric value encountered in /in/bu1Sf on line 13 array(3) { [0]=> array(4) { [0]=> string(1) "x" [1]=> string(0) "" [2]=> string(0) "" [3]=> string(1) "x" } [1]=> array(4) { [0]=> string(1) "y" [1]=> string(0) "" [2]=> string(0) "" [3]=> string(1) "y" } [2]=> array(4) { [0]=> string(1) "z" [1]=> string(0) "" [2]=> string(0) "" [3]=> string(1) "z" } }
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33
Notice: Use of undefined constant PREG_UNMATCHED_AS_NULL - assumed 'PREG_UNMATCHED_AS_NULL' in /in/bu1Sf on line 13 array(3) { [0]=> array(4) { [0]=> string(1) "x" [1]=> string(0) "" [2]=> string(0) "" [3]=> string(1) "x" } [1]=> array(4) { [0]=> string(1) "y" [1]=> string(0) "" [2]=> string(0) "" [3]=> string(1) "y" } [2]=> array(4) { [0]=> string(1) "z" [1]=> string(0) "" [2]=> string(0) "" [3]=> string(1) "z" } }

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