php获取两个中间字符串

给定字符串，开始字符和结束字符获取中间的字符串

function GetBetween($content,$start,$end){
    $r = explode($start, $content);
    if (isset($r[1])){
        $r = explode($end, $r[1]);
        return $r[0];
    }
    return '';
}
//演示范例：
GetBetween('foo test bar', 'foo', 'bar');
 
// --> returns ' test ';