Convert (or just get) the edited content to PHP var

Hi, I need your help:

I make a Website and have all like this:

<h3 contenteditable="true">
	title (php echo)
</h3>
<p contenteditable="true">
	some text (php echo)
</p>

The CKEditor toolbar is not visible while editing, but i want to save the content to database. I've created a button with php code that should work and i would be able to save it, if i would know, where to take the data from. I mean, I don't know, where the data is stored and how to convert it to PHP variable.

Could you please help me? I've searched and tried it since almost a week...

Thanks in advice.