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<?php $arr = array( 'arr1' => array( 'uids' => array('uid1','uid2','uid3','uid4'), 'dids' => array('did1','did2','did3','did4') ), 'arr2' => array( 'uids' => array('uid21','uid22','uid23','uid24'), 'dids' => array('did21','did22','did23','did24') ) ); $flatUids = array(); $flatDids = array(); $objTmp = (object) array('aFlat' => array()); array_walk_recursive($arr,function(&$v, $k, &$t){ if($k == 'uids') $t[] = $v; },$flatUids); var_dump($flatUids);

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