add_user_meta()

add_user_meta() — Adds meta data to a user. For historical reasons both the meta key and the meta value are expected to be “slashed” (slashes escaped) on input.

Inputs: $user_id (int): User ID. $meta_key (string): Metadata name. $meta_value (mixed): Metadata value. Arrays and objects are stored as serialized data and will be returned as the same type when retrieved. Other data types will be stored as strings in the database: false is stored and retrieved as an empty string (”) true is stored and retrieved as ‘1’ numbers (both integer and float) are stored and retrieved as strings Must be serializable if non-scalar. $unique (bool): Optional. Whether the same key should not be added. Default false.

Returns int|false: Meta ID on success, false on failure.