What is difference between #value and #markup?
#markup is 


  Used to set HTML that will be output on the form.


#value is


  Used to set values that cannot be edited by the user. Should NOT be confused with #default_value, which is for form inputs where users can override the default value.


For #value this might include submit buttons, hidden elements, etc. - basically anything that needs a value for the form submission, but where that value should not come from the user.

The only change you need to make in your sample code is to allow for the fact that classes in the attributes array must now be in an array themselves:

$form['in_title'] = array(
  '#type' =&gt; 'button',
  '#value' =&gt; t('ort'),
  '#executes_submit_callback' =&gt; false,
  '#attributes' =&gt; array('class' =&gt; array('hide-submit-exclude')),
);