PHPで正規表現を使用してimg srcを置き換える方法

/**
* 图片地址替换成压缩URL
* @param string $content 内容
* @param string $suffix 后缀
*/
function get_img_thumb_url($content="",$suffix="!c550x260.jpg")
{
// by http://www.manongjc.com/article/1319.html
$pregRule = "/<[img|IMG].*?src=[\&#39;|\"](.*?(?:[\.jpg|\.jpeg|\.png|\.gif|\.bmp]))[\&#39;|\"].*?[\/]?>/";
$content = preg_replace($pregRule, &#39;<img src="${1}&#39;.$suffix.&#39;" style="max-width:100%">&#39;, $content);
return $content;
}

//by http://www.manongjc.com
$content = &#39;<a href="#"><img class="center" src="https://xxx.com/styles/images/default.jpg"></a>&#39;
.&#39;<p><img class="center" src="https://img.xxx.com/images/219_Ig5eZI.jpg" style="max-width: 100%;"></p>&#39;;
$newct = get_img_thumb_url($content);
print_r($newct);

<a href="#"><img src="https://xxx.com/styles/images/default.jpg!c550x260.jpg" style="max-width:100%"></a><p><img src="https://img.xxx.com/images/219_Ig5eZI.jpg!c550x260.jpg" style="max-width:100%"></p>