How To Get Parent Category ID in Wordpress

In WordPress, retrieving the parent category ID of a specific category is a common requirement, especially when developing more complex themes or plugins. WordPress provides several built-in functions to help developers easily obtain this information. I will explain in detail how to use these functions with practical examples.

Method One: Using the get_term_by() Function

get_term_by() is a versatile function that retrieves information about any term type, including categories. To obtain the parent category ID of a category, you first need to know details about the child category, such as its ID, name, or slug.

Example Code:

php
// Assume we know the category's slug is 'child-category'
$category = get_term_by('slug', 'child-category', 'category');

// Verify if the category was found
if ($category !== false) {
    $parent_id = $category->parent;

    // Output the parent category ID
    echo 'Parent category ID is: ' . $parent_id;
} else {
    echo 'The specified category was not found';
}

In this example, we use the category's slug to fetch the category object and then read the parent property, which is an integer representing the parent category's ID.

Method Two: Directly Using the Category ID

If you already know the category's ID, you can directly use the get_category() function to retrieve the category object and then access its parent category ID.

Example Code:

php
// Assume we know the category's ID is 15
$category = get_category(15);

// Verify if the category was found
if ($category !== null) {
    $parent_id = $category->parent;

    // Output the parent category ID
    echo 'Parent category ID is: ' . $parent_id;
} else {
    echo 'The specified category was not found';
}

Method Three: Using WordPress Query Object

For more complex data handling during development—such as retrieving the parent ID of each category within a loop—you can use the WP_Query object or the get_categories() function to construct a category query. Then, iterate through the results to fetch each category's parent ID.

Example Code:

php
$args = array(
    'type'                     => 'post',
    'child_of'                 => 0,
    'parent'                   => '',
    'orderby'                  => 'name',
    'order'                    => 'ASC',
    'hide_empty'               => 1,
    'hierarchical'             => 1,
    'taxonomy'                 => 'category',
    'pad_counts'               => false
);

$categories = get_categories($args);

foreach ($categories as $category) {
    echo 'Category: ' . $category->name . ' - Parent category ID: ' . $category->parent . '<br />'; 
}

This code lists all categories along with their parent category IDs, which is invaluable for inspecting the structure or debugging.

Conclusion

Using WordPress's built-in functions—such as get_term_by(), get_category(), or combining get_categories() with loops—you can easily retrieve the parent category ID. Select the appropriate method based on your specific needs. I hope this information proves helpful for your project.