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<?php $arr = array(0 => array("key" => "val"), 1 => array("key" => "anotherval")); $key = "key"; $result = array_reduce($arr, function(&$cur, $item) use ($key) { return $cur=array_key_exists($key, $item)?$cur[]=$item[$key]:$cur; }, []); var_dump($result);

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