"Illegal choice full_html in Text format element" when submitting form programatically
You can try this.It works i think so

$form['formItem'] = array(
     '#type'=&gt;'text_format',
     '#title' =&gt; t('Field Label'),
     '#value' =&gt; 'This is my value',
     '#format'=&gt;'full_html',
);