Allow iFrame code to be entered in TinyMCE

dont-strip-iframes.php

<?php
/**
 * Below code could be placed inside your functions.php file
 *
 * Below is based on
 * http://codex.wordpress.org/Plugin_API/Filter_Reference/tiny_mce_before_init
 * and various places like
 * https://www.leighton.com/blog/stop-tinymce-in-wordpress-3-x-messing-up-your-html-code
 * http://redstarwebdevelopment.com/2011/07/15/iframes-in-wordpress/
 * http://www.lmhproductions.com/52/wordpress-tincymce-editor-removes-attributes/
 *
 */

add_filter( 'tiny_mce_before_init', 'jcars_leave_my_iframes_alone' );

function jcars_leave_my_iframes_alone( $settings ) {

	// If you need more parameters, add them to the list of approved ones between the square brackets
	$iframe_allow = 'iframe[id|class|title|style|align|frameborder|height|longdesc|marginheight|marginwidth|name|scrolling|src|width]';

	// Either add to the key or define it
	if ( empty ( $settings['extended_valid_elements'] ) ) {
		$settings['extended_valid_elements'] = $iframe_allow;
	} else {
		$settings['extended_valid_elements'] .= ',' . $iframe_allow;
	}

	// Send it back to let it do its thang
	return $settings;
}