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20 Useful WordPress Functions Every Developers Should Know

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WordPress is a powerful platform for Web development for developers as well as common users.  It has a great collection of functions which makes it an imperious tool with an easy learning curve.

Function files are commonly known as  functions.php file in a WordPress theme file. This file allows you to define each and every function. WordPress can be customized and offers the desired performance with exposure to hundreds of functions which is easy to install. 

In this blog, we will take a look into the popular WordPress functions every WordPress Developer should know as a professional.

List of WordPress Functions

  1. get_theme_mod()
  2. apply_filters()
  3. add_filter()
  4. get_option()
  5. esc_url()
  6. absint()
  7. get_template_part()
  8. is_singular()
  9. get_post_type()
  10. get_the_ID()
  11. the_content()
  12. have_posts()
  13. post_class()
  14. the_ID()
  15. get_permalink()
  16. get_the_title()
  17. get_footer()
  18. wp_nav_menu()
  19. add_section()
  20. current_user_can()

1. get_theme_mod()

Syntax 

get_theme_mod(string $name, string|false $default = false)

Usage

get_theme_mod() is used to filter the theme modification, retrieve all the theme modifications.

Add this below code in wp-includes/theme.php to do the same.

In header.php  add, 

2. apply_filters()

Syntax

apply_filters(string $tag, mixed $value)

Usage

This is a callback function that has to been added to a filter hook.  The callback functions attached to the filter hook are invoked by calling this function. apply_filters() function can be used to create a new filter hook by simply calling this function with the name of the new hook specified using the $tag parameter.

Add this below code in wp-includes/plugin.php.

3. add_filter()

Syntax

add_filter( string $tag, callable $function_to_add, int $priority = 10, int $accepted_args = 1)

Usage

It is called by themes/plugins, is used to add filters to the queue to be applied to the hook by core.

Add this below code in wp-includes/plugin.php

4. get_option()

Syntax

get_option( string $option, mixed $default = false )

Usage

It is used to check whether you need to install an option. get_option() is commonly used during the installation of plugin options and to test whether upgrading is required or not.

Add this below code in wp-includes/plugin.php

5. esc_url()

Syntax

esc_url( string $url, array $protocols = null, string $_context = ‘display’ )

Usage

It is used to clean and escape for output as a URL and to convert and fixe the HTML entities.  Sanitizes a string and removes disallowed URL protocols. Retrieve a list of protocols to allow in HTML attributes.

Add this below code in wp-includes/plugin.php

6. absint()

Syntax

absint( mixed $maybeint)

Usage

It used to convert a value into a non-negative integer.

Add this below code in wp-includes/functions.php

7. get_template_part()

Syntax

get_template_part( string $slug, string $name = null )

Usage

It includes a template part of the theme. Providing a simple mechanism for child themes to overload reusable sections of code in the theme.

Add the below code in wp-includes/general-template.php.

8. is_singular()

Syntax

is_singular>( string|array $post_types = ‘ ‘)

Usage

It determines whether the query is for an existing post under any page type (Blog post, attachment, page, custom post types). It enables you to target single-view pages, regular page pages, and the attachment page all in one swoop.

Add this below code to wp-includes/query.php

9. get_post_type()

Syntax

get_post_type( int|WP_Post|null $post = null )

Usage

It returns a string of the post type of the post ID or the current post, from this value you can check on the post type to decide what you do with it, just like the code.

Add the below code to the wp-includes/post.php

10. get_the_ID()

Syntax

get_the_ID()

Usage

It used to retrieve the ID of the current item in WordPress page.

Add the below code to the wp-includes/post-template.php

11. the_content()

Syntax

the_content( string $more_link_text = null, bool $strip_teaser =  false )

Usage

It is used to display the content in the editor in real time.

Add the below code to the wp-includes/post-template.php

12. have_posts()

Syntax

have_posts()

Usage

It is used to check the current WordPress query has any data to loop.  It will return true if data is available.

Add the below code to wp-includes/query.php

13. post_class()

Syntax

post_class( string|array $class = ‘ ‘, int|WP_Post $post_id = null )

Usage

It displays the classes for the post container element.

Add the below code to the wp-includes/post-template.php

14. get_sidebar()

Syntax

get_sidebar( string $name = null )

Usage

It is used to load the sidebar template.

Add the below code to wp-includes/general-template.php

15. get_permalink()

Syntax

get_permalink( int|WP_Post $post, bool $leavename = false )

Usage

It is used to get permalink for the current post or post ID.

Add the below code to wp-includes/link-template.php

16. get_the_title()

Syntax

get_the_title( int|WP_Post $post )

Usage

It is used to get the title of the posts.

Add the below code to wp-includes/post-template.php

17. get_footer()

Syntax

get_footer( string $name = null )

Usage

Used to load the footer template.

Add the below code to wp-includes/general-template.php

18. wp_nav_menu()

Syntax

wp_nav_menu( array $args =  array() )

Usage

It used to display a navigation menu.

Add the below code to wp-includes/nav-menu-template.php

19. add_section()

Syntax

add_section( WP_Customize_Section|string $id, array $args = array() )

Usage

This function is used to add your customize section.

Add the below code to wp-includes/class-wp-customize-manager.php

20. current_user_can()

Syntax

current_user_can( string $capability, mixed $args)

Usage

It is used to return, whether the current user with the specified capability.

Add the below code to the wp-includes/capabilities.php

Conclusion

There are more than 100+functions in WordPress, but the above listed are the popular ones among WordPress developers. You can use any of these functions on your WordPress development, share your experience. I’m glad to hear from you.  All these functions act as a plugin. They will be automatically loaded for both admin and frontend pages of WordPress sites.

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Written by
An enthusiastic PHP developer with 2+ years in IT. Wordpress, HTML, JavaScript, CSS are her grounds of expertise. She loves to create designs that resonate with the user and always has some thirst for new trends. Apart from coding, doing Handcrafts and artworks are her moment melting hobbies.

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