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<?php $asd = ['asd' => ['jkf' => ['qwe' => 'wer', 'asd' => '123', 'kjk' => 'sdf', '456' => 'zxc']], 'dfg', 'test' => ['ert' => '234'], 'cvf']; function recurse($array,$key=''){ static $output=[]; foreach($array as $k=>$v){ if(is_array($v)){ recurse($v,$key?$key.'['.$k.']':$k); }else{ $output[$key?$key.'['.$k.']':$k]=$v; } } return $output; } var_export(recurse($asd));
Output for 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 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.27, 8.4.1 - 8.4.14
array ( 'asd[jkf][qwe]' => 'wer', 'asd[jkf][asd]' => '123', 'asd[jkf][kjk]' => 'sdf', 'asd[jkf][456]' => 'zxc', 0 => 'dfg', 'test[ert]' => '234', 1 => 'cvf', )

preferences:
151.39 ms | 408 KiB | 5 Q