how can I write more embedded " and ' in php ? For example, I dunno how to write this html complete element with all apex:

As you can see, I use '' for the php string. Then inside, I use "", but then I need another level of apix and I dunno how to write that one in my php document. (php thinks that the string is complete in the middle because it sees another ' before the end.

$output .= '<img style="outline:none;" src="sites/default/unselect.png" alt="Unselect All" onclick='$(this).siblings('.form-item').each(function(index){ $('input:checkbox', this).attr('checked', ''); });'/>';

how can I solve this ?

thanks