set_image_alt_text_from_title

function set_image_alt_text_from_title($attachment_ID) {
    $attachment = get_post($attachment_ID);

    // Check if the attachment is an image
    if ($attachment && strpos($attachment->post_mime_type, 'image') !== false) {
        // Get the image's title
        $image_title = $attachment->post_title;
		$alt_text = str_replace("-"," ",$image_title);
        // Update the image's alt text with the title
        // Update the image's title with the alt text
        if ($alt_text && !empty($alt_text)) {
            wp_update_post(array(
                'ID' => $attachment_ID,
                'post_title' => $alt_text
            ));
        }
        update_post_meta($attachment_ID, '_wp_attachment_image_alt', $alt_text);
		
    }
}

add_action('add_attachment', 'set_image_alt_text_from_title');