PHP截取指定2个字符之间字符串的方法

<?php
function getNeedBetween($kw1,$mark1,$mark2){
$kw=$kw1;
$kw='123′.$kw.'123′;
$st =stripos($kw,$mark1);
$ed =stripos($kw,$mark2);
if(($st==false||$ed==false)||$st>=$ed)
return 0;
$kw=substr($kw,($st+1),($ed-$st-1));
return $kw;
}
?>

$keyword='查找(计组实验)'
$need=getNeedBetween($keyword, '(' , ')' );

结果： 

$need='计组实验';