Now Days WordPress is a popular blogging platform which have many inbuilt functions.For fetching wordpress categories, wordpress provide lots of inbuilt functions like get_categories(), wp_list_categories(), wp_dropdown_categories().   A. get_categories() Using This function we can fetch wordpress categories.

//Fetching categories in string format.
<?php
   get_categories(style=list&hide_empty=1);
?>

//Fetching categories in object format.
<?php
   $options = array('style' => 'list','hide_empty' => 1,);
   get_categories($options);
?>

  B. wp_list_categories() Using This function we can fetch wordpress categories in html format.

//Fetching categories in string format.
<?php
   wp_list_categories(style=list&hide_empty=1);
?>

//Fetching categories in object format.
<?php
   $options = array('style' => 'list','hide_empty' => 1,);
   wp_list_categories($options);
?>

  C. wp_dropdown_categories() Using This function we can fetch wordpress categories in dropdown list box.

//Fetching categories in string format.
<?php
   wp_dropdown_categories(style=list&hide_empty=1);
?>

//Fetching categories in object format.
<?php
   $options = array('style' => 'list','hide_empty' => 1,);
   wp_dropdown_categories($options);
?>