判断字符串并截取

//判断字符串中是否含有.f30.mp4 去掉并返回
$str = 'pc.podcasts.lizhi.cao.c64ed09517ebaa83195d15b8c6e85a4cc6c26c13.mp4.f30.mp4';
if (strpos($str, '.f30.mp4') !== false) {
    $str = substr($str, 0, -8);
}
echo $str;
//返回值 pc.podcasts.lizhi.cao.c64ed09517ebaa83195d15b8c6e85a4cc6c26c13.mp4