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<?php $strings = [ 'one"two_"_"_three', 'one__two_"__three', 'one__two_"__""____"three', 'one__two___"""""""______three', ]; var_export( preg_replace('~["_]+~', '_', $strings) );
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 - 8.1.34, 8.2.0 - 8.2.31, 8.3.0 - 8.3.31, 8.4.1 - 8.4.22, 8.5.0 - 8.5.7
array ( 0 => 'one_two_three', 1 => 'one_two_three', 2 => 'one_two_three', 3 => 'one_two_three', )

preferences:
104.58 ms | 1531 KiB | 4 Q