如何触发ZF2 HTML 5验证？

I'm using a custom button to submit my forms but want to take advantage of the HTML 5 validation. How can I trigger this validation prior to posting the data. I have two separate forms and would like to check the validation on both.

I see that the button has to reside in the form (prior to the close tag) in order for the validation to be triggered. Was wondering if there was a best practice is to do this?

This triggers the validation when added inside the form

<form>
...
 <button id="submitbutton" class="btn btn-warning" value="Submit" name="submit" type="submit">Submit</button>
</form>

I have one submit button for two forms.

Thanks, M