SimplePie_IRI::replace_invalid_with_pct_encoding PHP Метод

    function replace_invalid_with_pct_encoding($string, $valid_chars, $case = SIMPLEPIE_SAME_CASE)
    {
        // Normalise case
        if ($case & SIMPLEPIE_LOWERCASE) {
            $string = strtolower($string);
        } elseif ($case & SIMPLEPIE_UPPERCASE) {
            $string = strtoupper($string);
        }
        // Store position and string length (to avoid constantly recalculating this)
        $position = 0;
        $strlen = strlen($string);
        // Loop as long as we have invalid characters, advancing the position to the next invalid character
        while (($position += strspn($string, $valid_chars, $position)) < $strlen) {
            // If we have a % character
            if ($string[$position] === '%') {
                // If we have a pct-encoded section
                if ($position + 2 < $strlen && strspn($string, '0123456789ABCDEFabcdef', $position + 1, 2) === 2) {
                    // Get the the represented character
                    $chr = chr(hexdec(substr($string, $position + 1, 2)));
                    // If the character is valid, replace the pct-encoded with the actual character while normalising case
                    if (strpos($valid_chars, $chr) !== false) {
                        if ($case & SIMPLEPIE_LOWERCASE) {
                            $chr = strtolower($chr);
                        } elseif ($case & SIMPLEPIE_UPPERCASE) {
                            $chr = strtoupper($chr);
                        }
                        $string = substr_replace($string, $chr, $position, 3);
                        $strlen -= 2;
                        $position++;
                    } else {
                        $string = substr_replace($string, strtoupper(substr($string, $position + 1, 2)), $position + 1, 2);
                        $position += 3;
                    }
                } else {
                    $string = substr_replace($string, '%25', $position, 1);
                    $strlen += 2;
                    $position += 3;
                }
            } else {
                $replacement = sprintf("%%%02X", ord($string[$position]));
                $string = str_replace($string[$position], $replacement, $string);
                $strlen = strlen($string);
            }
        }
        return $string;
    }