Using WordPress ‘register_meta_args’ PHP filter

The ‘register_meta_args’ filter allows you to modify the registration arguments when registering meta in WordPress. This filter provides an opportunity to adjust default settings or add additional parameters to the metadata registration.

Usage

To use the ‘register_meta_args’ filter, you need to create a function with the desired changes and then hook it to the filter. Here’s a code example:

function my_register_meta_args( $args, $defaults, $object_type, $meta_key ) {
    // Your code here
}

add_filter( 'register_meta_args', 'my_register_meta_args', 10, 4 );

Parameters

• $args (array): Array of meta registration arguments.
• $defaults (array): Array of default arguments.
• $object_type (string): Type of object metadata is for. Accepts ‘post’, ‘comment’, ‘term’, ‘user’, or any other object type with an associated meta table.
• $meta_key (string): Meta key.

Examples

Make a meta field read-only

function make_meta_read_only( $args, $defaults, $object_type, $meta_key ) {
    if ( 'my_meta_key' === $meta_key ) {
        $args['readonly'] = true;
    }
    return $args;
}

add_filter( 'register_meta_args', 'make_meta_read_only', 10, 4 );

This example makes a meta field with the key ‘my_meta_key’ read-only by adding the ‘readonly’ argument and setting it to true.

Restrict a meta field to specific object types

function restrict_meta_to_object_type( $args, $defaults, $object_type, $meta_key ) {
    if ( 'restricted_meta_key' === $meta_key && 'post' !== $object_type ) {
        return false;
    }
    return $args;
}

add_filter( 'register_meta_args', 'restrict_meta_to_object_type', 10, 4 );

This example restricts the ‘restricted_meta_key’ meta field to be registered only for the ‘post’ object type.

Add a default value to a meta field

function add_default_meta_value( $args, $defaults, $object_type, $meta_key ) {
    if ( 'default_meta_key' === $meta_key ) {
        $args['default'] = 'Default value';
    }
    return $args;
}

add_filter( 'register_meta_args', 'add_default_meta_value', 10, 4 );

This example adds a default value ‘Default value’ to the meta field with the key ‘default_meta_key’.

Make a meta field required

function make_meta_required( $args, $defaults, $object_type, $meta_key ) {
    if ( 'required_meta_key' === $meta_key ) {
        $args['required'] = true;
    }
    return $args;
}

add_filter( 'register_meta_args', 'make_meta_required', 10, 4 );

This example makes a meta field with the key ‘required_meta_key’ required by adding the ‘required’ argument and setting it to true.

Add a custom validation callback to a meta field

function custom_meta_validation( $args, $defaults, $object_type, $meta_key ) {
    if ( 'custom_validation_meta_key' === $meta_key ) {
        $args['validate_callback'] = 'my_custom_validation_function';
    }
    return $args;
}

function my_custom_validation_function ( $value, $meta_key, $object_type ) { 
// Your validation logic here 
} 

add_filter( 'register_meta_args', 'custom_meta_validation', 10, 4 );

This example adds a custom validation callback to the meta field with the key ‘custom_validation_meta_key’. The ‘my_custom_validation_function’ function will be used to validate the meta value when it’s updated. Add your validation logic within this function.