求解数组序号及所在位置

$arr = array (  0 =>   array (    0 => 'SU14031300617',    'po_num' => 'SU14031300617',  ),  1 =>   array (    0 => 'SU14031300623',    'po_num' => 'SU14031300623',  ),  2 =>   array (    0 => 'SU14031300626',    'po_num' => 'SU14031300626',  ),  3 =>   array (    0 => 'SU14031300627',    'po_num' => 'SU14031300627',  ),  4 =>   array (    0 => 'SU14031300616',    'po_num' => 'SU14031300616',  ),  5 =>   array (    0 => 'SU14031300618',    'po_num' => 'SU14031300618',  ),  6 =>   array (    0 => 'SU14031300622',    'po_num' => 'SU14031300622',  ),  7 =>   array (    0 => 'SU14031300624',    'po_num' => 'SU14031300624',  ),  8 =>   array (    0 => 'SU14031300625',    'po_num' => 'SU14031300625',  ),)

foreach($arr as $k=>$tmp) {    if('SU14031300617' == $tmp[0]) {        return ($k+1) . '/' . count($arr);    }}return false;