wp-includes/class-wp-user.php:349Magic method for setting custom user fields.
$keystring$valuemixed public function __set( $key, $value ) { 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>' ) ); $this->ID = $value; return; } $this->data->$key = $value; }Introduced in 3.3.0. 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.