private function getQOP(): ?string
    {
        // Has the server specified any options for Quality of Protection
        if (\count($this->qop) > 0) {
            if ($this->options & self::OPTION_QOP_AUTH_INT) {
                if (\in_array('auth-int', $this->qop)) {
                    return 'auth-int';
                }
                if (\in_array('auth', $this->qop)) {
                    return 'auth';
                }
            }
            if ($this->options & self::OPTION_QOP_AUTH) {
                if (\in_array('auth', $this->qop)) {
                    return 'auth';
                }
                if (\in_array('auth-int', $this->qop)) {
                    return 'auth-int';
                }
            }
        }
        // Server has not specified any value for Quality of Protection so return null
        return null;
    }
private function getQOP(): ?string
    {
        // Has the server specified any options for Quality of Protection
        if (\count($this->qop) > 0) {
            if ($this->options & self::OPTION_QOP_AUTH_INT) {
                if (\in_array('auth-int', $this->qop)) {
                    return 'auth-int';
                }
                if (\in_array('auth', $this->qop)) {
                    return 'auth';
                }
            }
            if ($this->options & self::OPTION_QOP_AUTH) {
                if (\in_array('auth', $this->qop)) {
                    return 'auth';
                }
                if (\in_array('auth-int', $this->qop)) {
                    return 'auth-int';
                }
            }
        }
        // Server has not specified any value for Quality of Protection so return null
        return null;
    }
private function getQOP ( ) : ? string { // Has the server specified any options for Quality of Protection if ( \ count ( $ this -> qop ) > 0 ) { if ( $ this -> options & self :: OPTION_QOP_AUTH_INT ) { if ( \ in_array ( 'auth-int' , $ this -> qop ) ) { return 'auth-int' ; } if ( \ in_array ( 'auth' , $ this -> qop ) ) { return 'auth' ; } } if ( $ this -> options & self :: OPTION_QOP_AUTH ) { if ( \ in_array ( 'auth' , $ this -> qop ) ) { return 'auth' ; } if ( \ in_array ( 'auth-int' , $ this -> qop ) ) { return 'auth-int' ; } } } // Server has not specified any value for Quality of Protection so return null return null ; }
Returns the Quality of Protection to be used when authenticating with the server.

@return string this will either be auth-int or auth
Returns the Quality of Protection to be used when authenticating with the server .