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run code in 300+ PHP versions simultaneously
<?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));

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