错误的字符集get_error_message（）wordpress

There is PHP method in my API for handling POST requests:

...

$user_id = wp_create_user( $user_login, $user_pass, $user_login );

if ( is_wp_error( $user_id ) ) {
    $base_response['message'] = $user_id->get_error_message();
    $base_response['status'] = false;
    return json_encode ($base_response);
}

...

If user already exists, I get error message, but why this message ($base_response['message']) has unicode format: "u041du0430 u0436u0430u043bu044c, u0446u0435 u0456u043c'u044f u043au043eu0440u0438u0441u0442u0443u0432u0430u0447u0430 u0432u0436u0435 u0456u0441u043du0443u0454!". How to change this?

The problem was in cyrillic language for wordpress site and json_encode could not correctly convert cyrillic message. When I changed the language in the wordpress admin to English, everything is fine now.

You have wrong parameter in wp_create_user function. You need to pass Email in last parameter instead of user_login .

$user_id = wp_create_user( $user_login, $user_pass, $user_email );

if ( is_wp_error( $user_id ) ) {
    $base_response['message'] = $user_id->get_error_message();
    $base_response['status'] = false;
    return json_encode ($base_response);
}

Refer document for correct parameter : https://developer.wordpress.org/reference/functions/wp_create_user/