PhpHow-ToBeginner · 3 min read

How to Limit File Size in PHP Upload: Simple Guide

To limit file size in PHP uploads, set the upload_max_filesize and post_max_size directives in php.ini, and also check the file size in your PHP script using $_FILES['file']['size'] before processing the upload.

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Syntax

To limit file size in PHP uploads, you use two main parts:

php.ini settings: upload_max_filesize sets the max size for uploaded files, and post_max_size sets the max size for all POST data.
PHP script check: Use $_FILES['file']['size'] to check the uploaded file size and reject files that are too big.

php

; php.ini settings
upload_max_filesize = 2M
post_max_size = 8M

// PHP script check
if ($_FILES['file']['size'] > 2 * 1024 * 1024) {
    echo "File is too large.";
    exit;
}

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Example

This example shows how to limit an uploaded file to 1 megabyte (1MB) in PHP. It checks the file size and gives a message if the file is too big.

php

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    if (isset($_FILES['upload'])) {
        $maxFileSize = 1 * 1024 * 1024; // 1MB in bytes
        if ($_FILES['upload']['error'] === UPLOAD_ERR_OK) {
            if ($_FILES['upload']['size'] <= $maxFileSize) {
                echo "File uploaded successfully. Size: " . $_FILES['upload']['size'] . " bytes.";
                // Here you can move the file to a safe location
            } else {
                echo "Error: File size exceeds 1MB limit.";
            }
        } else {
            echo "Error: File upload error code " . $_FILES['upload']['error'];
        }
    } else {
        echo "No file uploaded.";
    }
} else {
    echo "Please upload a file.";
}
?>

<form method="post" enctype="multipart/form-data">
    <input type="file" name="upload" required>
    <button type="submit">Upload</button>
</form>

Output

Please upload a file.

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Common Pitfalls

Common mistakes when limiting file size in PHP uploads include:

Not setting post_max_size and upload_max_filesize in php.ini, which can silently block large uploads.
Only checking file size in PHP code but ignoring server limits, causing uploads to fail before your script runs.
Not handling upload errors properly, missing cases like partial uploads or no file sent.
Using client-side checks only, which can be bypassed easily.

php

<?php
// Wrong: No size check
if ($_FILES['file']['error'] === UPLOAD_ERR_OK) {
    echo "File uploaded without size check.";
}

// Right: Check size and error
$maxSize = 2 * 1024 * 1024; // 2MB
if ($_FILES['file']['error'] === UPLOAD_ERR_OK) {
    if ($_FILES['file']['size'] <= $maxSize) {
        echo "File accepted.";
    } else {
        echo "File too large.";
    }
} else {
    echo "Upload error.";
}

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Quick Reference

Summary tips to limit file size in PHP uploads:

Set upload_max_filesize and post_max_size in php.ini to your desired limits.
Check $_FILES['file']['size'] in your PHP script before processing.
Handle upload errors using $_FILES['file']['error'].
Use client-side checks for better user experience but never rely on them alone.

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Key Takeaways

Always set upload_max_filesize and post_max_size in php.ini to control max upload size.

Check the uploaded file size in PHP using $_FILES['file']['size'] to enforce limits.

Handle all upload errors by checking $_FILES['file']['error'] to avoid silent failures.

Client-side size checks improve UX but never replace server-side validation.

Remember post_max_size must be larger than or equal to upload_max_filesize.