这样获取数组值

这么获取数组值？
array(100) {
[0] => string(3) "1_1"
[1] => string(3) "2_1"
[2] => string(3) "2_2"
[3] => string(3) "3_1"
[4] => string(3) "3_2"
[5] => string(3) "3_3"
.....
}


输入"3_"就得
array(3) {
["0"] => string(1) "1"
["1"] => string(1) "2"
["2"] => string(1) "3"
请问这么取？
------解决思路----------------------

$data =array("1_1","2_1","2_2","3_1","3_2","3_3");
$need="3_";


$ret = array_filter($data,function($item) use($need){
	return strpos($item,$need) === 0;
});

var_dump($ret);

------解决思路----------------------

$d = array(
  "1_1",
  "2_1",
  "2_2",
  "3_1",
  "3_2",
  "3_3",
);
$in = '3_';
$out = array_values(
  array_map(function($s) use (&$in) {
    return substr($s, strlen($in));
  }, preg_grep("/$in/", $d))
);
print_r($out);

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
)