php如何将数组转xml字符串

  /**
 * 将一个数组转换为 XML 结构的字符串
 * @param array $arr 要转换的数组
 * @param int $level 节点层级, 1 为 Root.
 * @return string XML 结构的字符串
 */
public function array2xml($arr, $level = 1) {
    $s = $level == 1 ? "<xml>" : &#39;&#39;;
    foreach($arr as $tagname => $value) {
        if (is_numeric($tagname)) {
            $tagname = $value[&#39;TagName&#39;];
            unset($value[&#39;TagName&#39;]);
        }
        if(!is_array($value)) {
            $s .= "<{$tagname}>".(!is_numeric($value) ? &#39;<![CDATA[&#39; : &#39;&#39;).$value.(!is_numeric($value) ? &#39;]]>&#39; : &#39;&#39;)."</{$tagname}>";
        } else {
            $s .= "<{$tagname}>" . $this->array2xml($value, $level + 1)."</{$tagname}>";
        }
    }
    $s = preg_replace("/([\x01-\x08\x0b-\x0c\x0e-\x1f])+/", &#39; &#39;, $s);
    return $level == 1 ? $s."</xml>" : $s;
}