MathPHP\Functions\Polynomial::__toString PHP Метод

    public function __toString() : string
    {
        $variable = $this->variable;
        // Start with an empty polynomial
        $polynomial = '';
        // Iterate over each coefficient to generate the string for each term and add to the polynomial
        foreach ($this->coefficients as $i => $coefficient) {
            if ($coefficient == 0) {
                continue;
            }
            // Power of the current term
            $power = $this->degree - $i;
            // Build the exponent of our string as a unicode character
            $exponent = '';
            for ($j = 0; $j < strlen($power); $j++) {
                $digit = intval(strval($power)[$j]);
                // The j-th digit of $power
                $exponent .= self::SYMBOLS[$digit];
                // The corresponding unicode character
            }
            // Get the sign for the term
            $sign = $coefficient > 0 ? '+' : '-';
            // Drop the sign from the coefficient, as it is handled by $sign
            $coefficient = abs($coefficient);
            // Drop coefficients that equal 1 (and -1) if they are not the 0th-degree term
            if ($coefficient == 1 and $this->degree - $i != 0) {
                $coefficient = '';
            }
            // Generate the $term string. No $variable term if power = 0.
            if ($power == 0) {
                $term = "{$sign} {$coefficient}";
            } else {
                $term = "{$sign} {$coefficient}{$variable}{$exponent} ";
            }
            // Add the current term to the polynomial
            $polynomial .= $term;
        }
        // Cleanup front and back; drop redundant ¹ and ⁰ terms from monomials
        $polynomial = trim(str_replace([$variable . '¹ ', $variable . '⁰ '], $variable . ' ', $polynomial), '+ ');
        $polynomial = preg_replace('/^\\-\\s/', '-', $polynomial);
        $polynomial = $polynomial !== '' ? $polynomial : '0';
        return $polynomial;
    }