Adds a meta field to the given post.

Description

Post meta data is called "Custom Fields" on the Administration Screen.

Parameters

$post_idintrequired

Post ID.

$meta_keystringrequired

Metadata name.

$meta_valuemixedrequired

Metadata value. Must be serializable if non-scalar.

$uniquebooloptional

Whether the same key should not be added.

Default:false

Return

More Information

Note that if the given key already exists among custom fields of the specified post, another custom field with the same key is added unless the $unique argument is set to true, in which case, no changes are made. If you want to update the value of an existing key, use the update_post_meta() function instead

Character Escaping

Because meta values are passed through the stripslashes() function, you need to be careful about content escaped with \ characters. You can read more about the behavior, and a workaround example, in the update_post_meta() documentation.

Source

function add_post_meta( $post_id, $meta_key, $meta_value, $unique = false ) {
	// Make sure meta is added to the post, not a revision.
	$the_post = wp_is_post_revision( $post_id );
	if ( $the_post ) {
		$post_id = $the_post;
	}

	return add_metadata( 'post', $post_id, $meta_key, $meta_value, $unique );
}

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