shortcode for iframes

<?php

function custom_html_render_shortcode_wp543( $attr ){

    $id = ( isset( $attr['id'] ) && !empty( $attr['id'] ) ) ? sanitize_text_field( $attr['id'] ) : null;
    $width = ( isset( $attr['w'] ) && !empty( $attr['w'] ) ) ? sanitize_text_field( $attr['w'] ) : '160';
    $width .= 'px';
    $page = ( isset( $attr['page'] ) && !empty( $attr['page'] ) ) ? sanitize_text_field( $attr['page'] ) : null;

    ob_start();

    if( !$id ):
        echo '<div class="url-missing">Please, Enter a valid ID</div>';
    else: ?>

    <iframe style="width:100%; height:<?php echo esc_attr( $width ); ?>;" src="https://<?php echo esc_attr( $id ) ?>.exprealty.com/<?php echo esc_attr( $page ); ?>" allowtransparency="true" frameBorder="0"> </iframe>

    <?php endif;

    return ob_get_clean();

}
add_shortcode('exprealty-code','custom_html_render_shortcode_wp543');