[Resolved] Image validation code doesn't work!

[travelbuff]

Hello all:

I am working on a script that (among other things) uploads images. I am having a problem validating mime type. Here is the code snippet:

$filetype = $_FILES['grp_image_1']['type'];
 if ($filetype == ("image/jpeg" || "image/jpg" || "image/pjpeg" || "image/gif" || "image/png")) {
   echo '<BR>Valid image type, processing image... <BR>';
 } else {
   // the image is not a jpeg or gif
   echo '<BR>Only GIF and JPG images are supported<BR>';
   print_r($_FILES); //added for debugging
   unlink($_FILES['grp_image_1']['tmp_name']);
   exit ;
 } // end if-else for file type validation
// the file type is valid!

Problem is, this will validate any file type, even a text file!

When I just echo the file type, it echoes correctly.

What am I missing?

[drawmack]

$valid_types = array("image/jpeg","image/jpg","image/pjpeg","image/gif","image/png");
$filetype = $_FILES['grp_image_1']['type'];
 if (in_array($filetype,$valid_types)) {
   echo '<BR>Valid image type, processing image... <BR>';
 } else {
   // the image is not a jpeg or gif
   echo '<BR>Only PNG, GIF and JPG images are supported<BR>';
   print_r($_FILES); //added for debugging
   unlink($_FILES['grp_image_1']['tmp_name']);
   exit ;
 } // end if-else for file type validation
// the file type is valid!

[Mordecai]

A little explanation to what drawmack changed:

if ($filetype == ("image/jpeg" || "image/jpg" || "image/pjpeg" || "image/gif" || "image/png")) {

This line is the culprit. Basically, you're not telling it "if $filetype is a jpeg, a jpg, a pjeg, ..., then", you're telling it "if $filetype is (if the string "image/jpeg" is true or if the string "image/jpg" is true or...) then."

What drawmack did instead was tell it, "if the mimetype sent is one of these mimetypes, then", which is exactly what you want.

[drawmack]

Originally posted by Mordecai
A little explanation to what drawmack changed:

Great now they won't think that I am a mystic yogi from the himalayas thanks a lot Mordecai.

[travelbuff]

Hi Mordecai and drawmack:

drawmack's code worked like a charm, thanks! However, I am still confused. When I read drawmack's code, I understand why it works, but I still don't really understand why mine does not!

When I write:

$filetype = $_FILES['grp_image_1']['type']; 
if ($filetype == ("image/jpeg" || "image/jpg" || "image/pjpeg" || "image/gif" || "image/png")) 

Aren't I saying:
The value of $filetype is the string (whatever the mime type is);
If the value of $filetype equals jpeg or jpg or .... ?

If that is so, the value of $filetype should only match one of my strings if it's mime type is "valid", right? So if $_FILES['grp_image_1']['type'] returns the string "text/plain", and that string becomes the value of $filetype, there would be no match....

Please enlighten me, oh Yogi of the Himalayas...(or Mordecai 🙂 )

[drawmack]

To fix your statement it would have to be written like this

$filetype = $_FILES['grp_image_1']['type']; 
if ($filetype == "image/jpeg" || $filetype == "image/jpg" || $filetype == "image/pjpeg" || $filetype == "image/gif" || $filetype == "image/png")) 

The reason for this is that each section (piece between the || operators) is treated as a seperate and complete boolean statement.

In PHP, which is inherited from c, 0 is false and anything else is true. Since a string != 0 then a string is always true.

Now, $filetype != 0 so $filetype is true.

So when you look at it from the perspective of boolean logic what your if statement said was

if(TRUE == (TRUE || TRUE || TRUE || TRUE || TRUE)) {
//some code
}

Now do you see what it was always true?

[travelbuff]

Yes, makes perfect sense.

Thanks very much for your help!!