iframe-shortcode

// Add Shortcode
function request_system_form_shortcode( $atts ) {

	// Attributes
	$atts = shortcode_atts(
		array(
			'src' => 'http://chelan.highline.edu/~chloefitz/201/booking_v7.php?admin=T',
		),
		$atts,
		'request-system-form'
	);

	$output = '<iframe style="width:100%;max-width:100%;height:1000px" src="' . esc_url( $atts['src']  ) . '" class="request-form" frameborder="0" allowfullscreen></iframe>';
	
	return $output;

}
add_shortcode( 'request-system-form', 'request_system_form_shortcode' );