Скачать или смотреть Resolving HTTP 404 Errors When Using MPDF with PHP

Learn how to fix the `HTTP 404` error in MPDF by ensuring proper exception handling and folder permissions in your PHP application.
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This video is based on the question https://stackoverflow.com/q/63600565/ asked by the user 'Stijn Leenknegt' ( https://stackoverflow.com/u/356691/ ) and on the answer https://stackoverflow.com/a/63638667/ provided by the user 'Stijn Leenknegt' ( https://stackoverflow.com/u/356691/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting MPDF and HTTP 404 Errors

When working with PHP and generating PDFs using the MPDF library, encountering an HTTP 404 error can be frustrating, especially if things seem to work perfectly on your local development machine. This issue commonly occurs when the MPDF library is unable to process a request due to uncaught exceptions or inadequate file permissions. In this guide, we'll delve into why you might encounter this problem and how to effectively resolve it.

The Context of the Problem

You have successfully implemented MPDF on your local machine and tested it in your development environment. Everything runs smoothly, and you can generate PDFs without any issues. However, upon deploying your application to the server, you encounter an HTTP 404 response, indicating that the requested resource could not be found.

Your action code appears clean, and debugging features within MPDF seem to be functioning correctly on the local machine. But strangely, when uploaded to the server:

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the execution fails, causing an HTTP 404 error. Strangely, no entries are logged in the Apache error or access logs.

Understanding the Root Cause

Exception Handling in MPDF

It turns out the underlying issue may not directly be related to your application logic but rather with how MPDF handles errors. In MPDF, if certain exceptions are thrown during PDF generation—such as permission errors or memory limit issues—and they are not caught, it can manifest as an HTML 404 error instead of the expected HTTP 500 error.

Folder Permissions

Another common pitfall is permission settings on directories where MPDF attempts to write temporary files. If the MPDF library does not have write access to the designated temporary folder, it won’t be able to generate the PDF, leading to errors.

Resolution Steps

To resolve this issue, follow these steps to ensure that the MPDF library functions correctly on your server:

1. Check Exception Handling

Implement a try-catch block around your MPDF instantiation and usage. This will help catch any exceptions thrown by MPDF and provide more descriptive error handling.

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2. Check Directory Permissions

Ensure that the directory used for temporary files has the correct permissions. On a Linux server, you can set permissions with the following command:

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You might also need to ensure that the web server user has ownership of this folder.

3. Verify Other PHP Settings

Confirm that all necessary PHP extensions are installed and enabled on your server. This includes libraries such as GD, mbstring, and others which are required by MPDF.

4. Check Server Error Logs

Always check the server's error logs for any messages related to MPDF. This can provide further insights into what might be failing.

Conclusion

Generating PDFs can sometimes lead to unexpected errors, but with a systematic approach, you can identify and fix these problems. By ensuring proper exception handling and directory permissions in your MPDF implementation, you can prevent those frustrating HTTP 404 errors from occurring on your production server. Happy coding!