PHP-Spell-Check can be set to spell check the contents of any HTML element such as a DIV, SPAN, IFRAME in your page. Such an element must have inner HTML or a value attribute. Just set the Fields property the SpellCheckButton Class to the Id attribute of you element.
Note that PHPSpellCheck is XML and HTML aware - so it can spell-check next tags without altering markup structure.
Inline spellchecking using thea SpellAsYouType Class is not possible for HTML elements.
$mySpell->Fields = "ElementId";
$mySpell->Fields = "ElementId1,ElementId2,ElementId3";