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<?php foreach ( array( array('/\\d+/', '$0'), array('/\\d+/', '$01'), array('/\\d+/', '$001'), array('/\\d+/', '${0}1'), array('/(\\d+)/', '$0'), array('/(\\d+)/', '$01'), array('/(\\d+)/', '{$0}1'), array('/(\\d+)/', '$1'), array('/(\\d+)/', '$12'), array('/(\\d+)/', '$012'), array('/(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(\\d+)/', '$12'), array('/(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(\\d+)/', '$123'), ) as $list ) { list ($re, $replace) = $list; echo "$re '$replace' => '", preg_replace($re, $replace, "42"), "'\n"; }
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.5, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.30, 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 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
/\d+/ '$0' => '42' /\d+/ '$01' => '' /\d+/ '$001' => '421' /\d+/ '${0}1' => '421' /(\d+)/ '$0' => '42' /(\d+)/ '$01' => '42' /(\d+)/ '{$0}1' => '{42}1' /(\d+)/ '$1' => '42' /(\d+)/ '$12' => '' /(\d+)/ '$012' => '422' /(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(\d+)/ '$12' => '42' /(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(\d+)/ '$123' => '423'
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 /\d+/ '$0' => '42' /\d+/ '$01' => '' /\d+/ '$001' => '421' /\d+/ '${0}1' => '421' /(\d+)/ '$0' => '42' /(\d+)/ '$01' => '42' /(\d+)/ '{$0}1' => '{42}1' /(\d+)/ '$1' => '42' /(\d+)/ '$12' => '' /(\d+)/ '$012' => '422' /(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(\d+)/ '$12' => '42' /(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(^)(\d+)/ '$123' => '423'
preferences:
285.54 ms | 402 KiB | 412 Q