PHP test for corrupt (but apparently fine) images - php

Question

I have a simple image upload script that uses SimpleImage.php
(http://www.white-hat-web-design.co.uk/blog/resizing-images-with-php/)
to resize and save 2 copies of an uploaded image.
There isn't a massive amount of validation, just checking that it exists and that the file extension is fine, and also an exif_imagetype(); call.
This has worked with no problems so far until I tried to upload a seemingly normal jpeg which turned out to be invisibly (and untestably?) corrupt. There was something not right about it, but I know very little about image corruption - it looked fine and opened no problem on anything, but when I tried to save a scaled copy in my script I got a white page.
The problem is definitely that specific image, I've tested exhastively with other images both from my local stock and from stock image sites, and only that one image breaks it.
I resized a copy using Photoshop (the predicted file size thingy gave me some wierd numbers - 45meg for top quality jpeg) and that uploaded with no issues.
So my question is, how do I test for this?
The image in question is here: http://chinawin.co.uk/broken.jpg //beware, 700k
notes: I've tested with similar resolutions, image sizes and names, everything else worked apart from this image.
UPDATE:
Through trial and error I've narrowed down where the script breaks to the line where I load the image into a var for SimpleImage. Strangely this is the second line that does so (the first being to create the large copy, this one to create a thumbnail).
Commenting it out means the rest works ok... perhaps some refactoring will avoid this problem.
2nd Update:
Here's a snippet of code and some context from the line that fails:
//check if our image is OK
if ($image && $imageThumb)
{
//check if image is a jpeg
if (exif_imagetype($_FILES[$k]['tmp_name']) == IMAGETYPE_JPEG)
{
list($width, $height, $type, $attr) = getimagesize($_FILES[$k]['tmp_name']);
//echo 1;
$image = new SimpleImage();
//echo 2;
$image->load($_FILES[$k]['tmp_name']);
//echo 3;
$imageThumb = new SimpleImage();
//echo 4;
//this next line topples my script, but only for that one image - why?:
$imageThumb->load($_FILES[$k]['tmp_name']);
//echo '5<br/><br/>-------<br/>';
//do stuff, save & update db, etc
}
}
Final edit:
Turns out my script was running out of memory, and with good reason - 4900x3900 image with 240 ppi turns out to be around 48 meg when loaded into memory, twice - so I was using probably > 90meg of ram, per image.
Hats off to #Pekka for spotting this.
Refactoring the script to only have the image loaded once, and then this variable used instead of it's sibling, fixed my script. Still having (different) issues with upoading larger (2.5meg) images but this is for another question.

Answer 1

This is most likely a memory issue: Your JPG is very large (more than 4000 x 4000 pixels) and, uncompressed, will indeed eat up around 48 Megabytes of RAM.
Activate error reporting to make sure. If it's the reason, see e.g. here on what to do: Uploading images with PHP and hitting the script memory limit