Unable to add a submit button to a drupal Block
A small change needed as below


  
  Key was to chnage the type from button to submit
  But I guess making a separate function to get the form will be better
  


function block_content() {

  //calling the form in the block
  $block_contents = drupal_get_form('_cacheclearbutton_clear_cache_form');

  return $block_contents;
}

// A separate function to return the form to clear the cache
function _cacheclearbutton_clear_cache_form() {
  $form = array();
  $form['clearbutton'] = array(
    '#type' =&gt; 'submit',
    '#value' =&gt; 'Clear Cache by Module Test',
    '#submit' =&gt; array('clearbutton_submit'),
  );
  return $form;
}

function clearbutton_submit($form, &amp;$form_state) {
  cache_clear_all();
  drupal_set_message(t('Setting a message from the submit handler'));
}