PHP查找字符串中所有出现的子字符串

在不使用正则表达式的情况下，类似这样的方法应该可以返回字符串位置：

$html = "dddasdfdddasdffff";$needle = "asdf";$lastPos = 0;$positions = array();while (($lastPos = strpos($html, $needle, $lastPos))!== false) {    $positions[] = $lastPos;    $lastPos = $lastPos + strlen($needle);}// Displays 3 and 10foreach ($positions as $value) {    echo $value ."<br />";}