[PHP知识库]php正则替换img标签中的alt属性为空

 function replace_img_alt($str)
    {
        if (empty($str)) {
            return $str;
        }
        $str = htmlspecialchars_decode($str);
        preg_match_all('/<img[\s\S]*?src\s*=\s*[\"|\'](.*?)[\"|\'][\s\S]*?>/i', $str, $result, PREG_SET_ORDER);
        $pattern = '/(<img.*?)alt=(["\']).*?\2([^>]+>)/is';
        $replacement = "\$1$3";
        $resultCount = count($result);
        for ($i = 0; $i < $resultCount; $i++) {
            if (strpos($result[$i][1], '.swf') === false) {
                $img[] = $result[$i][1];
                //$imgStr = "<img src='" . $result[$i][1] . "' />";
                $imgStr = preg_replace($pattern, $replacement, $result[$i][0]);
                $str = str_replace($result[$i][0], $imgStr, $str);
            }
        }
 
        return htmlspecialchars($str);
    }