Add text after input field with form api (field-suffix)
You can use the #field_suffix property for exactly that:


  Text or code that is placed directly after a textfield. This can be used to add a unit to a textfield.


For example:

$form['a_textfield'] = array(
  '#type' =&gt; 'textfield',
  '#title' =&gt; t('A Label'),
  '#size' =&gt; 10,
  '#maxlength' =&gt; 15,
  '#description' =&gt; t('A Field description'),
  '#required' =&gt; TRUE,
  '#field_suffix' =&gt; 'Suffix'
);