wp-includes/class-wp-user.php:379Magic method for unsetting a certain custom field.
$keystring public function __unset( $key ) { if ( 'id' === $key ) { _deprecated_argument( 'WP_User->id', '2.1.0', sprintf( /* translators: %s: WP_User->ID */ __( 'Use %s instead.' ), '<code>WP_User->ID</code>' ) ); } if ( isset( $this->data->$key ) ) { unset( $this->data->$key ); } if ( isset( self::$back_compat_keys[ $key ] ) ) { unset( self::$back_compat_keys[ $key ] ); } }Introduced in 4.4.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wp-user.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.