Helper function for getting widths and url's of all the available sizes of an image in WordPress.

get_image_widths_and_urls.php

/**
 * Helper function for getting the widths and url's of all the available crops of an image.
 * @param  Number $id: The id of the image that you need the info for
 * @return Array An associative array with array["widths"] containing an array of widths and array["urls"] containing the corresponding image urls.
 */
function get_image_widths_and_urls($id) {
    //Get all the possible image sizes
    $image_size_array = get_intermediate_image_sizes();
    //error_log('--------------------$image_size_array------------------------');
    //error_log( var_export($image_size_array, true) );

    $image_width_array = [];
    //$image_url_array = [];
    $widths_and_urls = [];
    $i = 0;
    foreach ( $image_size_array as $image_size_name ) {
        $image_info_array = wp_get_attachment_image_src($id, $image_size_name);
        $image_url = $image_info_array[0];
        $image_width = $image_info_array[1];
        if ( $image_width >= 300 ) { //Don't want to include any images smaller than 300px, since they won't really ever be useful
            $image_width_array[] = $image_width;
            $widths_and_urls[$i] = [
                "width" => $image_width,
                "url" => $image_url,
            ];
            //error_log('--------------------$image_info_array------------------------');
            //error_log( var_export($image_info_array, true) );
            $i++;
        }
    }
    array_multisort ($image_width_array, SORT_ASC, SORT_NUMERIC, $widths_and_urls); //Sorts $widths_and_urls by the "width" key

    return $widths_and_urls;
}