All 7 File Upload Handling questions
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How does PHP handle file uploads submitted through an HTML form, and what information does the $_FILES superglobal provide? How do you move an uploaded file from its temporary location to a permanent storage location using move_uploaded_file? How should you validate an uploaded file's type and size before accepting it, and why is checking only the file extension considered insufficient for security? How should uploaded file names be sanitized and randomized to avoid security risks and naming conflicts when storing files on the server? What security risks arise from allowing file uploads into a publicly accessible directory, and how do you prevent uploaded files from being executed as scripts? How should a large scale application design its file upload architecture to handle high volumes of uploads reliably, including virus scanning and offloading storage to a dedicated service?
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PHP › File Upload Handling

How do you handle multiple file uploads submitted from a single form field, and what does the resulting $_FILES array structure look like?

Intermediate

Answer

When a file input is configured to accept multiple files using an array style field name, the $_FILES superglobal organizes the data slightly differently, storing each attribute, such as name or tmp_name, as its own array containing one entry per uploaded file, meaning you typically need to loop through these parallel arrays using a shared numeric index to process each individual uploaded file correctly.
<input type="file" name="documents[]" multiple>

foreach ($_FILES['documents']['name'] as $index => $name) {
    $tmpPath = $_FILES['documents']['tmp_name'][$index];
    move_uploaded_file($tmpPath, 'uploads/' . $name);
}
Real-world example A photo gallery upload feature lets users select and upload several images at once, looping through the resulting parallel arrays in $_FILES to process and store each individual uploaded photo correctly.

Common follow-ups: How does this array structure change if you use a modern framework's file upload handling instead of raw $_FILES?;What happens if a user selects zero files for a multiple file upload input?

Form Handling & Validation;Basics & Types
All 7 File Upload Handling questions