Function and usage of add_comment_meta() in wordpress


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    The add_comment_meta() function in WordPress is used to add custom metadata to a specific comment. This function is particularly useful when you need to store extra information about comments that is not provided by WordPress by default. Here's a detailed explanation of its usage:

    Function Signature

    add_comment_meta( int $comment_id, string $meta_key, mixed $meta_value, bool $unique = false ): int|false


    1. $comment_id (int, required): This is the ID of the comment to which you want to add metadata. This ID uniquely identifies each comment in the WordPress database.

    2. $meta_key (string, required): This is the name of the metadata field you want to add. It acts as a key for the metadata.

    3. $meta_value (mixed, required): This is the value of the metadata you are adding. It can be of any type, but if it's not a scalar value (like array or object), it must be serializable.

    4. $unique (bool, optional): This parameter determines whether the same key should not be added if it already exists for the comment. If set to true, the function will not add the same key for the same comment if it already exists. The default value is false.

    Return Value

    • The function returns the meta ID (integer) on success. This ID is a unique identifier for the newly added metadata.
    • It returns false if the operation fails for any reason, such as if the comment ID doesn't exist or if there's a database error.

    Sample Usage

    Here's an example of how you might use add_comment_meta():

    $comment_id = 123; // Assume this is a valid comment ID
    $meta_key = 'favorite_color';
    $meta_value = 'blue';
    $unique = true;
    $result = add_comment_meta($comment_id, $meta_key, $meta_value, $unique);
    if ($result === false) {
        echo 'Failed to add comment meta.';
    } else {
        echo 'Comment meta added successfully. Meta ID: ' . $result;

    In this example, we are adding a custom metadata field favorite_color with the value blue to the comment with ID 123. We set $unique to true to ensure that this metadata key-value pair is not duplicated for the same comment.

    Important Notes

    • Security Considerations: Always validate and sanitize the $meta_value if it's coming from user input to prevent security vulnerabilities.
    • Use Cases: This function is particularly useful in plugins or themes where you need to extend the functionality of comments by adding additional data, such as ratings, flags, or custom identifiers.

    Remember, this function is part of WordPress's Plugin API, and it requires a WordPress environment to work. It's not a standalone PHP function.

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