How to Determine if a User Has Uploaded a File in PHP?

Determining User File Upload in PHP

When implementing form validation for file uploads, handling optional uploads is crucial. To distinguish between a submitted form without an upload and a validation failure, it is necessary to verify the presence of an uploaded file.

Checking for File Upload with is_uploaded_file()

To determine whether a user has uploaded a file, you can use the is_uploaded_file() function. This function returns TRUE if a file exists with the specified filename and was uploaded via HTTP POST.

Usage:

<code class="php">if (!file_exists($_FILES['myfile']['tmp_name']) || !is_uploaded_file($_FILES['myfile']['tmp_name'])) {
    echo 'No upload';
}</code>

This code checks if a file is both present in the temporary directory ($_FILES['myfile']['tmp_name']) and was uploaded as expected. If either condition is not met, it indicates that no file was uploaded.

Additional Considerations

• The file_exists() check is necessary because some web servers do not create the temporary file if the upload fails.
• The is_uploaded_file() function is designed to prevent malicious users from exploiting the script to work on unauthorized files.
• For further validation, you can also check the $_FILES['myfile']['size'] to ensure that the file is not empty.

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