Mayank Tripathi

Understanding Serialization in WordPress: What, Why, and How

Serialization in WordPress is a fundamental concept that plays a crucial role in how data is stored and retrieved from the database. It’s a process that converts complex data types, such as arrays and objects, into a string format that can be easily stored in the database and later retrieved. Let’s dive into what serialization is, why WordPress uses it, and how it affects your work as a developer.

What is Serialization?

Serialization is the process of converting a data structure—such as an array or object—into a format that can be easily stored or transmitted. In PHP, this involves converting the data into a string representation that maintains its structure, allowing it to be restored to its original form later.

For example, an array like:

$my_array = array(69);

When serialized, it becomes:

a:1:{i:0;i:69;}

This serialized string represents the original array, preserving its structure and data.

Why Does WordPress Use Serialization?

WordPress uses serialization to ensure that complex data types can be stored in the database without losing their structure. This is particularly important for storing data in the wp_options, wp_postmeta, and wp_usermeta tables, where serialized data allows arrays and objects to be safely stored and retrieved.

When you use functions like update_post_meta, update_option, or add_user_meta, WordPress automatically serializes any array or object before storing it in the database. Similarly, when you retrieve this data using get_post_meta, get_option, or get_user_meta, WordPress unserializes the data, converting it back into the original array or object.

How Serialization Affects Your Work

As a developer, understanding serialization is key to working effectively with WordPress. Here are a few important points to keep in mind:

  • Automatic Serialization: When you store arrays or objects using WordPress’s built-in functions, serialization happens automatically. For example:
$photos = array(69);
update_post_meta($post_id, 'rt-media-meta-img', $photos);

This array will be serialized and stored in the database as a:1:{i:0;i:69;}.

  • Retrieving Serialized Data: When you retrieve this data, WordPress automatically unserializes it:
$photos = get_post_meta($post_id, 'rt-media-meta-img', true);
// $photos will be an array: array(69)

This means you usually don’t need to worry about serialization when getting data, as WordPress handles it for you.

  • Potential Pitfalls: There are a few situations where serialization can cause issues, such as when trying to perform direct database queries on serialized data. Since serialized data is stored as a string, it’s not easily searchable or filterable with standard SQL queries.
  • Alternatives to Serialization: If you need to avoid serialization for any reason, you can use JSON encoding/decoding as an alternative:
$json_photos = json_encode($photos);
update_post_meta($post_id, 'rt-media-meta-img', $json_photos);
//Later, you can decode it:
$photos = json_decode($json_photos, true);

Why Validate Capabilities?

WordPress has a set of predefined capabilities that correspond to various actions users can perform. Common capabilities include:

  • edit_posts
  • publish_posts
  • delete_posts
  • edit_pages
  • manage_options

When you pass a capability to the user_can() function, it’s essential to ensure that the capability is valid and recognized by WordPress. Failing to do so can lead to unexpected behavior or errors, especially when capabilities are dynamically generated or come from user input.

The Problem with Undetermined Capabilities

If you pass a variable directly to the user_can() function without validating it, you might encounter a PHPCS warning like:


WordPress.WP.Capabilities.Undetermined: Couldn't determine the value passed to the $capability parameter in function call to user_can(). Please check if it matches a valid capability. Found: $permission

This warning highlights that the capability being checked is not recognized, which could indicate a potential issue in your code.

A Safe Approach: Validating Capabilities

To avoid such warnings and ensure the capability is valid, you can create a function that checks the capability against a list of known, valid capabilities. Here’s how you can do it:

function is_valid_capability( $capability ) {
    // List of known capabilities
    $valid_capabilities = array(
        'edit_posts',
        'edit_others_posts',
        'publish_posts',
        'delete_posts',
        'edit_pages',
        'edit_others_pages',
        'publish_pages',
        'delete_pages',
        // Add other known capabilities here
    );

    return in_array( $capability, $valid_capabilities, true );
}

This function checks if the capability is among the list of recognized capabilities. You can expand this list based on the capabilities used in your application.

Implementing the Validation

Before passing the capability to user_can(), validate it using the is_valid_capability() function:






$permission = 'edit_posts'; // Example permission, should be dynamic in real cases

if ( is_valid_capability( $permission ) ) {
    if ( ! empty( $user ) ) {
        $user_id = $user[0]; // Get the first user ID from the array
        $user_obj = get_user_by( 'id', $user_id ); // Retrieve the user object

        if ( $user_obj && user_can( $user_obj, $permission ) ) {
            // User has the valid permission
            return true;
        }
    }
} else {
    // Invalid capability
    return false;
}

// User not found or does not have the valid permission
return false;






This approach ensures that only valid capabilities are checked, preventing errors and ensuring that your code adheres to best practices.