使用PHP上传WebM文件的问题

I want to be able to upload WebM files on my server from a simple upload script. I currently am able to successfully upload jpg's and png's to the server as well as write them to my sql database, but when using WebM, the file fails to be succesfully uploaded. However, it does create a filename and redirect me to that file, but it obviously doesn't exist. Here is the section of code for uploading WebM files. Any help would be appreciated.

                    if($file['type'] == "video/webm")
                    {
                        $seed = str_split('abcdefghijklmnopqrstuvwxyz'.'ABCDEFGHIJKLMNOPQRSTUVWXYZ'); // and any other characters
                        shuffle($seed);
                        $rand = '';
                        foreach (array_rand($seed, 6) as $k) 
                        $rand .= $seed[$k];
                        $filename = $rand.".webm";
                        $dir = "uploads/".$filename;

                        while(file_exists($dir))
                        {
                            $seed = str_split('abcdefghijklmnopqrstuvwxyz'.'ABCDEFGHIJKLMNOPQRSTUVWXYZ'); // and any other characters
                            shuffle($seed);
                            $rand = '';
                            foreach (array_rand($seed, 6) as $k) 
                            $rand .= $seed[$k];
                            $filename = $rand.".webm";
                            $dir = "u/".$filename;  
                        }
                            $host="localhost";
                            $username=""; 
                            $password=""; 
                            $db_name="removed"; 
                            $tbl_name="removed"; 
                            $ipaddress = $_SERVER['REMOTE_ADDR'];

                            mysql_connect("$host", "$username", "$password")or die("cannot connect server "); 
                            mysql_select_db("$db_name")or die("cannot select DB");

                            $datetime=date("y-m-d h:i:s");
                            $sql="INSERT INTO $tbl_name(filename, datetime)VALUES('$filename', '$datetime')";
                            $result=mysql_query($sql);
                            mysql_close();

                            move_uploaded_file($file['tmp_name'], $dir);
                            header( 'Location: u/'.$filename ) ;


                    }

I assume it has to do with the way I define the filetype, but i can't find any good information on the internet about it. Is video/webm the correct definition? I don't know.

Thanks.