{"id":85876,"date":"2023-05-17T15:55:15","date_gmt":"2023-05-17T15:55:15","guid":{"rendered":"\/tutorials\/?p=85876"},"modified":"2025-04-23T09:17:33","modified_gmt":"2025-04-23T09:17:33","slug":"wordpress-add-filter","status":"publish","type":"post","link":"\/tutorials\/wordpress-add-filter\/","title":{"rendered":"What Are Filters in WordPress and How to Use WordPress add_filter\u00a0"},"content":{"rendered":"

A WordPress filter is a hook that manipulates internal data before it is displayed on the browser. To create a filter, add the add_filter <\/strong>function in your website’s functions.php <\/strong>file.<\/p>

In WordPress development, users use this filter to modify a plugin, a theme, or specific website functionality. For example, you can change your website posts’ excerpt length or add a footer note to the articles.<\/p>

In this WordPress tutorial, we will explain how to use the add_filter <\/strong>function to create a filter hook. We will also explore the function’s parameters and provide its common use case examples.<\/p>

Download all-in-one WordPress cheat sheet<\/a><\/p>

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\n What Is a WordPress Filter?\n <\/p>\n <\/div>\n


\nA WordPress filter is a hook that modifies data before it is returned to the database and displayed to the users. As a result, you can customize plugins, themes, or websites’ functionality without altering the WordPress core files.
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\nFor example, add a footnote to all website posts or change their excerpt length. There are four common filter hook functions – add_filter<\/strong>, remove_filter<\/strong>, has_filter<\/strong>, and doing_filter<\/strong>.<\/p><\/div>\n\n\n\n<\/p>

How WordPress Filters Work<\/h3>

In short, filters intercept data that WordPress passes. They modify it based on the given function and display it to users’ web browsers. To help you understand, look at this snippet:<\/p>

\/\/ Specify the filter and the callback function\n   add_filter( 'example_filter', 'example_callback' );\n   \/\/ Define the callback function\n   function example_callback( $example ) {\n      \/\/ alter $example by concatenating on it\n      $example . ‘ add a text at the end ’;\n      return $example;\n   }<\/pre>
Here’s the explanation of the example:<\/p>
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  1. Set a filter using the add_filter <\/strong>function that will modify the data. In our case, the filter name is example_filter<\/strong>.<\/li>\n\n\n\n
  2. Define the callback function that will run when WordPress finds the filter, namely example<\/strong>_callback<\/strong>.<\/li>\n\n\n\n
  3. Specify how the callback function will modify the data, which the $example<\/strong> argument represents. In the snippet, we will use the full stop to concatenate it with a sentence at the end.<\/li>\n\n\n\n
  4. Display the modified data to the user’s web browser using the return <\/strong>method.<\/li>\n<\/ol>
    To apply a filter hook to your WordPress website, write the code in your currently-active theme’s functions.php <\/strong>file. If you use Hostinger’s WordPress hosting service<\/a>, open File Manager <\/strong>and navigate to public_html\/wp-content\/themes\/yourthemefolder<\/strong>.<\/p>
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    \"The<\/a><\/figure>\n<\/div>
    Furthermore, we recommend adding the code to your child theme’s<\/a> file to prevent it from disappearing after an update. Alternatively, create a separate file for the filter hooks in the theme root folder and write the following code in the functions.php <\/strong>file<\/a> to call it:<\/p>
    include _once( get_template_directory(), ‘\/yourfilename.php’:’<\/pre>
    If you can’t access the theme root folder, install a plugin<\/a> to add the custom code directly from your WordPress admin dashboard. A popular plugin for this task is Code Snippets<\/a>.<\/p>
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    \n            \n                \n                    \n                <\/svg>\n                Important\n            <\/span>\n            
    \n                Important!<\/strong> Modifying the functions.php<\/strong> file may lead to an error or an inaccessible website. To avoid this, create a backup<\/a> before proceeding.\n            <\/p><\/div>\n\n\n\n<\/p>
    WordPress add_filter Parameters<\/h2>
    The WordPress add_filter <\/strong>function has four parameters. Here’s each of them:<\/p>