Choose a file to upload: <input name="uploadedfile" type="file" />
   <br />
      Username:<input type="text" name="username">
   <br />
      Password:<input type="text" name="password">
   <br />
      FaxNumber:<input type="text" name="faxnumber">

   <input type="submit" value="Upload File" />

if ($_FILES["file"]["type"] == "image/gif"){
    //do stuff here
}
else{
    //the file was wrong type handle error here
}

$_FILES['yourFileName']['type']

by default: nearly anything you want (pdf,txt,exe,jpg) etc.