Never Trust MIME Types Alone

MIME types can be forged. Ensure real file validation:

$allowed = ["image/jpeg","image/png"];
if (!in_array($_FILES["file"]["type"], $allowed)) {
 die("Invalid file format.");
}

Validate Extensions & Scan Contents

Double-check with pathinfo() and use scanning tools where possible.

Restrict Upload Size

ini_set("upload_max_filesize", "5M");
ini_set("post_max_size", "6M");

Store Files Outside Public Root

Serve using a PHP proxy script for safety.

Randomised Filenames

Never expose user’s original file name directly to the web.

These steps prevent malicious scripts being uploaded and executed.