PHP Debugging: How to view image resource information

Question

I am debugging a PHP application that handles image resources. I would like to see the output ($dst_image as per the PHP manual's jargon), but the code is not in a place that I could simply output it to the browser. Would the best debugging procedure be to write $dst_image to a file, and to load that file in the browser? Any other ideas?

Thanks.

Why can't you output to a browser? An echo anywhere should do that. — Jungle Hunter
– Jungle Hunter, Commented Apr 23, 2012 at 15:15
I cannot output to a browser as other code has already output text to a browser. The image-handling bit happens in the background. If the application used output buffering I could do it, but also it cannto be refactored as such. — dotancohen
– dotancohen, Commented Apr 23, 2012 at 15:32

Alex · Accepted Answer · 2012-04-23 19:00:59Z

1

See Example #1 and #2, imagejpeg will output the jpeg data.

You need to do few tings:

set headers for image header('Content-Type: image/jpeg');
output your image data
Make sure you are not outputting any data except the image

At the end you should end up with something like this:

<?php

// Get new dimensions
// Resample
// etc...

// set header so browser can render image properly
header('Content-Type: image/jpeg');

// Output
imagejpeg($image, null, xxx);
// [or] 
echo file_get_contents($pathToJpgImage);

If you find your self in a situation where current request outputs data and you cannot output image... You can inject the base64 encoded image data into the HTML by using <img src="data:image/jpeg;base64,..." />. See php documentation on base64_encode for images.

edited Apr 23, 2012 at 19:00

answered Apr 23, 2012 at 15:23

Alex

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4 Comments

dotancohen Over a year ago

Thank you, but for technical reasons (output already sent) the image cannot be simple sent to the browser unless there is a way to negate all the text previously output.

dotancohen Over a year ago

Although I doesn't address the issue that I bring up, I am accepting this as the accepted answer as it is the canonical solution for the general case. When this solution doesn't work, then one must write the image to a file, as I had suspected. Thank you Alex.

Alex Over a year ago

@dotancohen my apologies, it was not clear to me from your question... See 2nd part of my answer, it should do the trick.

dotancohen Over a year ago

Alex, that is terrific! It is exactly the fix that I needed but was afraid would not exist! That is a clever and creative solution, I would call it witty if one could describe code as such. Thank you!

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