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<?php mb_ereg('(?<word>\w+)', '国', $matches); print_r($matches);
Output for 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.30, 8.2.0 - 8.2.25, 8.3.0 - 8.3.13
Array ( [0] => 国 [1] => 国 [word] => 国 )
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33
Array ( [0] => 国 [1] => 国 )
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65.83 ms | 407 KiB | 5 Q