PHP代码：去除EM标签，保留内容

将下面这段代码，改为只删除em>和/em>和和这四个标签，不删除标签中间的内容

$ai_article_html = preg_replace('/<(/)?em>/', '', $ai_article_html);

This code uses regular expression to remove only the '' and '' tags without removing the content between them.