create_unifi_admin.php

public function create_site_admin(
        $name, 
        $email,
        $password
    ) {
        $payload = [
            'cmd'         => 'create-admin',
            'name'        => trim($name),
            'email'       => trim($email),
            'x_password'    => trim($password),
            'requires_new_password' => false,
            'readonly' => false,
            'for_sso' => false,
            'device_adopt' => false,
            'device_restart' => true,
            'role' => 'admin',
            'permissions' => []
        ];

        // Allow device restart, may not work but that's ok I guess!
        $payload['permissions'][] = 'API_DEVICE_RESTART';

        return $this->fetch_results_boolean('/api/s/' . $this->site . '/cmd/sitemgr', $payload);

    }