Write a PHP script to compute addition of two matrices as a form input.

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $matrix1 = json_decode($_POST["matrix1"], true);
    $matrix2 = json_decode($_POST["matrix2"], true);
    
    $rows = count($matrix1);
    $cols = count($matrix1[0]);
    $result = [];
    
    for ($i = 0; $i < $rows; $i++) {
        for ($j = 0; $j < $cols; $j++) {
            $result[$i][$j] = $matrix1[$i][$j] + $matrix2[$i][$j];
        }
    }
    echo "Result: " . json_encode($result);
}
?>

<!DOCTYPE html>
<html>
<body>
    <br>
    <form method="post">
    Matrix 1:
    <input type="text" name="matrix1" placeholder='[[1,2],[3,4]]' required><br>
    Matrix 2:
    <input type="text" name="matrix2" placeholder='[[5,6],[7,8]]' required><br>
    <input type="submit" value="Compute">
    </form>
</body>
</html>