How Can I Reliably Determine File Types of Uploaded Files in PHP?

Determining File Types of Uploaded Files in PHP

Securing your website against malicious file uploads requires verifying the types of files users submit. However, conventional methods like is_uploaded_file() and move_uploaded_file() offer limited file type checking.

Users can often bypass mime type checking due to inaccuracies or by intentionally altering them. Extension checks face similar issues, as tampering with extensions is trivial. Image-specific methods like getimagesize() are ineffective for other file types.

For a more comprehensive approach, consider the following solutions:

• mime_content_type and Fileinfo: These PHP commands analyze file contents to determine their type.
• System Command: Running "file -bi $uploadedfile" using PHP's system() function can provide accurate type identification, assuming system("file -bi $uploadedfile") delivers reliable results on your server.

While each method has its advantages and limitations, these techniques offer enhanced file type verification to protect your website from potentially harmful uploads.

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