How to pass the value of the text_format field of the user form with PHP code in drupal 7 for further recording in the database?

Question

Drupal

It is necessary in the settings of your own module to implement saving the value of the text_format field with the php code.
module mymodule. The file mymodule.module generates module settings with the form:

function mymodule_form($form, &$form_state, $arr = null) {
...
      $form['tmpl_code'] = array(
            '#type' => 'text_format',                                            
            '#title' => t('PHP code'),
            '#format' => 'php_code',
      );
...
}

function mymodule_form_submit($form, &$form_state)
{
  $arr = array(
    ...
    'php_code' 		=> $form_state['values']['php_code'],
    ...
  );
  ...
  drupal_write_record('mymodule', $arr);  //Здесь ошибка
  ...	
  }
  ...
}

The error occurs when saving to the database. What is the correct way to save php code to the module table of this value using Drupal methods? How to wrap the contents of a tmpl_code textbox when saving it with drupal_write_record?
Thank you.