title: WordPress get user by meta data
body: <p>How can I retrieve all users registered in my WordPress blog having a particular meta data?</p>
  
  <p>For example I have made an option to add a custom meta data for every registering users having meta key as <code>parent_id</code>. If I want to list all users having <code>parent_id</code> as <code>2</code> , then how can I do this?</p>