Can't extract the contents of $_FILES using exif_read_data

Question

I am just new to using php and have been totally stumped for the last several days. I am trying to extract and use the Key-value pairs extracted from multiple arrays in the $_FILES. I am sure this is a ridiculously dumb question but I am stumped. if I run the following code I get the following results.

$exif = exif_read_data('/uploads/'.$file['name'],  0, true);

  foreach($_FILES as $file){
  echo $file['name']  .  " :<br />\n";
  foreach ($exif as $key => $section) {
      foreach ($section as $name => $val) {

          echo "<pre>This is \$name" . $name ."<br>";
          echo "<pre>This is \$val" . $val ."<br>";
          }
        }
     } 

The following is the output:

Uploaded Image

Image contains headers  
Across the Field - LK.jpg :
FILE.FileName: Across the Field - LK.jpg
FILE.FileDateTime: 1361055472  
FILE.FileSize: 294785  
FILE.FileType: 2  
FILE.MimeType: image/jpeg  
FILE.SectionsFound: ANY_TAG, IFD0, THUMBNAIL, EXIF  
COMPUTED.html: width="700" height="525"  
COMPUTED.Height: 525  
COMPUTED.Width: 700  
COMPUTED.IsColor: 1  
COMPUTED.ByteOrderMotorola: 0  
COMPUTED.ApertureFNumber: f/9.0  
COMPUTED.Copyright: Copyright 2010   
IFD0.ImageWidth: 1024  
IFD0.ImageLength: 768  
IFD0.BitsPerSample: Array  
IFD0.PhotometricInterpretation: 2  
IFD0.Model: NIKON D300  
IFD0.Orientation: 1  
IFD0.SamplesPerPixel: 3  
IFD0.XResolution: 720000/10000 
IFD0.YResolution: 720000/10000    
IFD0.ResolutionUnit: 2  
IFD0.Software: Adobe Photoshop CS5 Windows  
IFD0.DateTime: 2013:01:24 16:33:16  
IFD0.Artist: lken  
IFD0.Copyright: Copyright 2010   
IFD0.Exif_IFD_Pointer: 316  
THUMBNAIL.Compression: 6
THUMBNAIL.XResolution: 72/1  
THUMBNAIL.YResolution: 72/1 
THUMBNAIL.ResolutionUnit: 2  
THUMBNAIL.JPEGInterchangeFormat: 642  
THUMBNAIL.JPEGInterchangeFormatLength: 0  
EXIF.ExposureTime: 1/100  
EXIF.FNumber: 9/1  
EXIF.ISOSpeedRatings: 400  
EXIF.ExifVersion: 0221  
EXIF.DateTimeOriginal: 2010:08:15 05:57:17  
EXIF.DateTimeDigitized: 2010:08:15 05:57:17 
EXIF.ShutterSpeedValue: 6643856/1000000   
EXIF.ApertureValue: 633985/100000  
EXIF.FocalLength: 1700/100  
EXIF.ColorSpace: 65535  
EXIF.ExifImageWidth: 700   
EXIF.ExifImageLength: 525  

For brevity sake I left out the data from the second photo.

The following is the output of $_FILES:

Array
(
    [userfile] => Array
        (
            [name] => Across the Field - LK.jpg
            [type] => image/jpeg
            [tmp_name] => C:\wamp\tmp\php223.tmp
            [error] => 0
            [size] => 294785
        )

    [userfile1] => Array
        (
            [name] => autumn-panorama - lk.jpg
            [type] => image/jpeg
            [tmp_name] => C:\wamp\tmp\php224.tmp
            [error] => 0
            [size] => 106349
        )
)

I have looked on every site and in every book I can find to find how to access the name value pairs (such as IFD0.ImageWidth: 1024 and IFD0.ImageLength: 768 ) so I can set restrictions on upnload sizes etc.

I am now very confused and will appreciate any help or direction. Resources are especially appreciated. Thank you.

Answer 1

Well, that code snippet already does the job, hence for your first file, you should be able to do the below.

$exif = exif_read_data($_FILES['userfile']['tmp_name'],  0, true);

if (isset($exif['IFD0']['ImageWidth']) && isset($exif['IFD0']['ImageLength']))
{
    // good to go!
    $width = $exif['IFD0']['ImageWidth'];
    $height = $exif['IFD0']['ImageLength'];
}
else
{
    // size data not present, fallback onto something else
    return;
}

Now, with that said, you should not trust the exif data to do your constraint validation! Exif data are metadata. They can be spoofed/injected easily, or not be there at all. Instead do an analysis of the actual image data, by firstly checking file size itself, and then using getimagesize() for example. See http://www.php.net/manual/en/function.getimagesize.php