$_FILES for file uploads in PHP

Introduction

$_FILES helps you get information about files users upload through a form. It makes handling uploads easy.

When you want users to upload profile pictures on your website.

When you need to let users submit documents or PDFs.

When building a form that accepts multiple images for a gallery.

When you want to save uploaded files on your server.

When you want to check the size or type of an uploaded file before saving.

Syntax

PHP

$_FILES['input_name']['property']

input_name is the name attribute of the file input in your HTML form.

property can be name, type, tmp_name, error, or size.

Examples

Gets the original name of the uploaded file from the input named 'photo'.

PHP

$_FILES['photo']['name']

Gets the size in bytes of the uploaded file from the input named 'document'.

PHP

$_FILES['document']['size']

Gets the temporary file path where PHP stored the uploaded file before you move it.

PHP

$_FILES['avatar']['tmp_name']

Sample Program

This program shows a simple file upload form. When you pick a file and submit, it prints the file name and size if the upload worked.

PHP

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    if (isset($_FILES['myfile']) && $_FILES['myfile']['error'] === 0) {
        $filename = $_FILES['myfile']['name'];
        $filesize = $_FILES['myfile']['size'];
        echo "File uploaded: $filename<br>";
        echo "Size: $filesize bytes<br>";
    } else {
        echo "No file uploaded or there was an error.";
    }
}
?>

<form method="post" enctype="multipart/form-data">
  <label for="myfile">Choose a file:</label>
  <input type="file" name="myfile" id="myfile">
  <button type="submit">Upload</button>
</form>

Important Notes

Always use enctype="multipart/form-data" in your form tag to allow file uploads.

Check $_FILES['input_name']['error'] to make sure the upload succeeded before using the file.

Files are stored temporarily on the server. Use move_uploaded_file() to save them permanently.

Summary

$_FILES holds info about uploaded files from a form.

Use the file input's name to access its data in $_FILES.

Check for errors and file size before saving the file.

Practice

1. What does the $_FILES superglobal in PHP store?

easy

A. Database connection details

B. User session data

C. Information about files uploaded via an HTML form

D. Server environment variables

Solution

1. Step 1: Understand the purpose of $_FILES

   $_FILES is a special PHP variable that holds details about files uploaded through a form.

2. Step 2: Compare with other options

   User session data is stored in $_SESSION, database details are not stored here, and server variables are in $_SERVER.

3. Final Answer:

   Information about files uploaded via an HTML form -> Option C

4. Quick Check:

   $_FILES = Uploaded file info [OK]

Hint: Remember: $_FILES always relates to uploaded files [OK]

Common Mistakes:

• Confusing $_FILES with $_SESSION
• Thinking $_FILES holds server info
• Assuming $_FILES stores form text inputs

2. Which of the following is the correct way to access the name of an uploaded file with input name userfile?

easy

A. $_FILES['userfile']['filename']

B. $_FILES['userfile']['file']

C. $_FILES['userfile']['file_name']

D. $_FILES['userfile']['name']

Solution

1. Step 1: Recall the structure of $_FILES

   Each uploaded file's info is stored in an array with keys like 'name', 'type', 'tmp_name', 'error', and 'size'.

2. Step 2: Identify the correct key for the original filename

   The key for the original filename is 'name', not 'filename' or 'file_name'.

3. Final Answer:

   $_FILES['userfile']['name'] -> Option D

4. Quick Check:

   Filename key = 'name' [OK]

Hint: Use 'name' key to get original filename from $_FILES [OK]

Common Mistakes:

• Using 'filename' or 'file_name' instead of 'name'
• Confusing keys with other $_FILES elements
• Trying to access $_POST for file names

3. What will the following PHP code output if a file named 'photo.jpg' is uploaded successfully?

if ($_FILES['pic']['error'] === 0) {
    echo $_FILES['pic']['name'];
} else {
    echo 'Upload failed';
}

medium

A. photo.jpg

B. Upload failed

C. 0

D. Undefined index error

Solution

1. Step 1: Check the error code for the uploaded file

   An error code of 0 means the upload was successful with no errors.

2. Step 2: Output the original filename

   Since error is 0, the code echoes the original filename stored in $_FILES['pic']['name'], which is 'photo.jpg'.

3. Final Answer:

   photo.jpg -> Option A

4. Quick Check:

   Error 0 means success, so filename prints [OK]

Hint: Error 0 means success; print 'name' to get filename [OK]

Common Mistakes:

• Assuming error 0 means failure
• Printing error code instead of filename
• Not checking if 'pic' index exists

4. Identify the error in this PHP snippet handling file upload:

if ($_FILES['upload']['error'] == 0) {
    move_uploaded_file($_FILES['upload']['name'], 'uploads/' . $_FILES['upload']['name']);
    echo 'File saved';
} else {
    echo 'Error uploading';
}

medium

A. Not checking file size before moving

B. Using 'name' instead of 'tmp_name' in move_uploaded_file

C. Checking error with == instead of ===

D. Missing semicolon after echo statement

Solution

1. Step 1: Understand move_uploaded_file parameters

   The first parameter must be the temporary file path stored in tmp_name, not the original filename.

2. Step 2: Identify the incorrect usage

   The code incorrectly uses $_FILES['upload']['name'] as the source file, which is wrong and causes failure.

3. Final Answer:

   Using 'name' instead of 'tmp_name' in move_uploaded_file -> Option B

4. Quick Check:

   move_uploaded_file needs tmp_name as source [OK]

Hint: Use 'tmp_name' as source file in move_uploaded_file [OK]

Common Mistakes:

• Using original filename instead of temp file path
• Ignoring error codes before moving files
• Not validating file size or type

5. You want to save an uploaded file only if it is less than 2MB and has no errors. Which code snippet correctly checks these conditions before moving the file?

if (/* condition here */) {
    move_uploaded_file($_FILES['file']['tmp_name'], 'uploads/' . $_FILES['file']['name']);
    echo 'Upload successful';
} else {
    echo 'Upload failed';
}

hard

A. if ($_FILES['file']['error'] === 0 && $_FILES['file']['size'] < 2097152)

B. if ($_FILES['file']['error'] == 1 || $_FILES['file']['size'] > 2097152)

C. if ($_FILES['file']['error'] !== 0 && $_FILES['file']['size'] <= 2097152)

D. if ($_FILES['file']['error'] === 0 || $_FILES['file']['size'] > 2097152)

Solution

1. Step 1: Check for no upload errors

   The error code must be exactly 0 to confirm no errors during upload.

2. Step 2: Check file size limit

   The file size must be less than 2MB (2 * 1024 * 1024 = 2097152 bytes).

3. Step 3: Combine conditions correctly

   Both conditions must be true, so use logical AND (&&) with strict equality and less-than size check.

4. Final Answer:

   if ($_FILES['file']['error'] === 0 && $_FILES['file']['size'] < 2097152) -> Option A

5. Quick Check:

   Error 0 and size < 2MB = correct check [OK]

Hint: Use error === 0 and size < 2MB with && [OK]

Common Mistakes:

• Using || instead of && for conditions
• Checking error != 0 instead of === 0
• Confusing size units or limits