content-type failing in firefox when using dynamic images (PHP) in <img src="source.php">

Okay excuse the cryptic subject.

I have a system which dynamically fetches image data and does some modification on the fly.

Essentially, missing out the unimportant bits, this is my code:

$File->Filename = "testimage.jpg";
$File->Open();
$FileData = 开发者_运维技巧$File->Read();

header('Content-Type: image/jpeg');

echo $FileData;

The only output on the page is $FileData. Okay. When I run the script as is, Firefox presents me with a blank page and Chrome and IE give me a 'missing picture' box.

However oddly enough, when I remove the Content Type declaration, I can see the raw image data just fine. I have tested this with several images, granted all of the JPEG type but it clearly loads up the different pictures just fine, as the raw data changes successfully, and matches the raw content of the image itself.

Anyone have any idea why it would be failing to just display the image at this point?

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You need to give more information in order to let the browser handle it correctly (use the correct type and length):

header('Content-Length: '.strlen($FileData),true); // EDIT: inserted the strlen function as suggested by kgb
header('Content-Type: image/jpeg');

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Try setting Content-Length appropriately. Remove the trailing ?> to make sure there is no whitespace at the end of the script and ensure that the starting it at the very start of your script.

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i'll combine phant0m's and Thariama's answers ;):

header('Content-Length: '.strlen($FileData), true);
header('Content-Type: image/jpeg');
die($FileData);