Convert images to .webp

functions.php

<?php
add_filter('wp_handle_upload', 'convert_to_webp', 10, 2);

function convert_to_webp($upload, $context) {
    $file_path = $upload['file'];
    $file_info = pathinfo($file_path);
    $extension = strtolower($file_info['extension']);
    $allowed_extensions = ['jpeg', 'jpg', 'png', 'gif'];

    if (in_array($extension, $allowed_extensions)) {
        $image = null;
        switch ($extension) {
            case 'jpeg':
            case 'jpg':
                $image = imagecreatefromjpeg($file_path);
                break;
            case 'png':
                $image = imagecreatefrompng($file_path);
                break;
            case 'gif':
                $image = imagecreatefromgif($file_path);
                break;
        }

        if ($image) {
            $webp_path = $file_info['dirname'] . '/' . $file_info['filename'] . '.webp';
            if (imagewebp($image, $webp_path, 80)) {
                imagedestroy($image);
                unlink($file_path);
                $upload['file'] = $webp_path;
                $upload['url'] = str_replace($file_info['basename'], $file_info['filename'] . '.webp', $upload['url']);
                $upload['type'] = 'image/webp';
            }
        }
    }

    return $upload;
}