Get image alt text in WordPress

get_image_alt.php

<?php
// Get image alt text
function aproch_image_alt($image_id) {
    $image_title = get_the_title($image_id);
    $image_alt = get_post_meta( $image_id, '_wp_attachment_image_alt', true);
    echo !empty($image_alt) ? $image_alt : $image_title;
}