php 上传文件类型判断函数(避免上传漏洞 )

function ($file_name,$pass_type=array('jpg','jpeg','gif','bmp','png')){
$yx_file = $pass_type;
$kzm = substr(strrchr($file_name,"."),1);
$is_img = in_array(strtolower($kzm),$yx_file);
if($is_img){
return true;
}else{
return false;
}
}