Proper Way To Validate MIME Type Of Files While Handling File Uploads In PHP

In this article, I will show you a cool tip on how to properly validate the file MIME types even if they change the extension of the file.

I will cover the following in this article

1. Basic HTML Form
2. General Old Way Validation (Probably Wrong Way)
3. The Right Way To Validate MIME Type ( finfo )
4. Different MIME Extensions Link

---

Prerequisites

Basic knowledge on PHP. Even if you don't know how to upload the files and handle it then I have written an article on it:

How To Uploads Files In PHP?

How To Upload Image In PHP?

---

1) Basic HTML Form

This is very basic HTML form make sure you have enctype="multipart/form-data"

<form action="store_product.php" method="post" enctype="multipart/form-data">
    <div>
        <input type="file" name="product_invoice" id="product_invoice">
    </div> <br>
    <div>
        <input type="submit" value="Create Product">
    </div>
</form>

---

2) General Old Way Validation (Probably Wrong Way)

From the above form when you select the image and upload it will go to store_product.php PHP file which will handle the file upload with validation.

Following is the snippet code which demonstrates the file validation

/** Store the file details in variable */
$product_invoice    = $_FILES['product_invoice'];

/** Uploaded file name */
$file_name          = $product_invoice['name'];
$file_tmp           = $product_invoice['tmp_name'];

/** Using pathinfo() to get the file extension of file */
$pathinfo           = pathinfo($file_name);
$extension          = $pathinfo['extension'];

/** Allowed extensions */
$file_extensions    = ['pdf', 'xls', 'jpeg', 'jpg', 'png', 'svg', 'webp'];

/** Check File extensions */
if(!in_array($extensio
n, $file_extensions)){
    $errors[] = 'File allowed extensions '. implode(', ', $file_extensions);
}

The above is wrong because we are validating based on file extension. Because someone may upload video & change just the extension to jpeg or pdf.

---

3) The Right Way To Validate MIME Type ( finfo )

To properly validate the file MIME you need to use finfo which internally uses finfo_open

Basically you use it the following way

/** Using finfo to just get the MIME type */
$finfo      = new finfo(FILEINFO_MIME_TYPE);

/** You will get extension along with the mime types */
$extension  = $finfo->file($file_tmp);

Full detailed on the same as follows

/** Store the file details in variable */
$product_invoice    = $_FILES['product_invoice'];

/** Uploaded file name */
$file_name          = $product_invoice['name'];
$file_tmp           = $product_invoice['tmp_name'];

/** Allowed MIME extensions */
$file_extensions    = ['image/jpeg', 'image/pjpeg', 'application/pdf'];

/** Using finfo to just get the MIME type */
$finfo      = new finfo(FILEINFO_MIME_TYPE);

/** You will get extension along with the mime types */
$extension  = $finfo->file($file_tmp);

/** Check File extensions */
if(!in_array($extension, $file_extensions)){
    $errors[] = 'File allowed extensions '. implode(', ', $file_extensions);
}

---

4) Diff MIME Extensions Link

I don't want to reinvent the wheel. So here is the link for the CODEIGNITER FRAMEWORK MIME TYPES

---

Conclusion

Hope you liked the article. If yes then please do share with your friends.

Articles For You

Factory States For Clean And Fluent Laravel Testing

Upload Image In PHP?

Writing Clean Code In PHP

PHP extension ext-intl * is missing

Generate Sitemap in PHP Laravel

Send Email In PHP With PHPMailer

New Features In Laravel 8

Simple Way To Create Resourceful API Controller In Laravel

Free SSL Certificate With Lets Encrypt/Certbot In Linux (Single / Multiple Domains)

Hotlink Protection In Nginx

Send SMS With Amazon SNS (Simple Notification Service) Using PHP

Google reCAPTCHA Integration In PHP Laravel Forms

Upload Multiple Files In PHP?

Setup AMP (Accelerated Mobile Pages) In PHP Laravel

Use Different PHP Versions In Ubuntu / Linux