Sometimes the use of ' is recommended because single quotes (') and double quotes (") are used in a construction. However, use of ' in XHTML should generally be avoided for compatibility reasons. IE7 will give a runtime error on '. You can use numeric character reference ' instead.

Following example shows the use of &#39 in combination with link_to_function:

<?php echo link_to_function(image_tag('printer.png', 'alt=Print page friendly') . ' Print', 'printUrl(&#39;/page/print/id/'.$page->getId().'&#39;)') ?>