title: How do I fix the error of call to undefined function for add_settings_field()?
body: <p>I followed exactly <a href="http://wp.tutsplus.com/tutorials/theme-development/the-complete-guide-to-the-wordpress-settings-api-part-2-sections-fields-and-settings/" rel="nofollow noreferrer">this tutorial</a> and I got this error:</p>
  
  <blockquote>
    <p>Fatal error: Call to undefined function add_settings_field() in
    /home/content/41/11334041/html/test/wp-content/themes/mothereffintheme/functions.php
    on line 47</p>
  </blockquote>
  
  <p>I'm new to working with the Wordpress API and I don't have any idea to how to fix it.</p>