Requests_IRI::replace_invalid_with_pct_encoding() WordPress Method

	protected function replace_invalid_with_pct_encoding($string, $extra_chars, $iprivate = false) {
		// Normalize as many pct-encoded sections as possible
		$string = preg_replace_callback('/(?:%[A-Fa-f0-9]{2})+/', array($this, 'remove_iunreserved_percent_encoded'), $string);

		// Replace invalid percent characters
		$string = preg_replace('/%(?![A-Fa-f0-9]{2})/', '%25', $string);

		// Add unreserved and % to $extra_chars (the latter is safe because all
		// pct-encoded sections are now valid).
		$extra_chars .= 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~%';

		// Now replace any bytes that aren't allowed with their pct-encoded versions
		$position = 0;
		$strlen = strlen($string);
		while (($position += strspn($string, $extra_chars, $position)) < $strlen) {
			$value = ord($string[$position]);

			// Start position
			$start = $position;

			// By default we are valid
			$valid = true;

			// No one byte sequences are valid due to the while.
			// Two byte sequence:
			if (($value & 0xE0) === 0xC0) {
				$character = ($value & 0x1F) << 6;
				$length = 2;
				$remaining = 1;
			}
			// Three byte sequence:
			elseif (($value & 0xF0) === 0xE0) {
				$character = ($value & 0x0F) << 12;
				$length = 3;
				$remaining = 2;
			}
			// Four byte sequence:
			elseif (($value & 0xF8) === 0xF0) {
				$character = ($value & 0x07) << 18;
				$length = 4;
				$remaining = 3;
			}
			// Invalid byte:
			else {
				$valid = false;
				$length = 1;
				$remaining = 0;
			}

			if ($remaining) {
				if ($position + $length <= $strlen) {
					for ($position++; $remaining; $position++) {
						$value = ord($string[$position]);

						// Check that the byte is valid, then add it to the character:
						if (($value & 0xC0) === 0x80) {
							$character |= ($value & 0x3F) << (--$remaining * 6);
						}
						// If it is invalid, count the sequence as invalid and reprocess the current byte:
						else {
							$valid = false;
							$position--;
							break;
						}
					}
				}
				else {
					$position = $strlen - 1;
					$valid = false;
				}
			}

			// Percent encode anything invalid or not in ucschar
			if (
				// Invalid sequences
				!$valid
				// Non-shortest form sequences are invalid
				|| $length > 1 && $character <= 0x7F
				|| $length > 2 && $character <= 0x7FF
				|| $length > 3 && $character <= 0xFFFF
				// Outside of range of ucschar codepoints
				// Noncharacters
				|| ($character & 0xFFFE) === 0xFFFE
				|| $character >= 0xFDD0 && $character <= 0xFDEF
				|| (
					// Everything else not in ucschar
					   $character > 0xD7FF && $character < 0xF900
					|| $character < 0xA0
					|| $character > 0xEFFFD
				)
				&& (
					// Everything not in iprivate, if it applies
					   !$iprivate
					|| $character < 0xE000
					|| $character > 0x10FFFD
				)
			) {
				// If we were a character, pretend we weren't, but rather an error.
				if ($valid) {
					$position--;
				}

				for ($j = $start; $j <= $position; $j++) {
					$string = substr_replace($string, sprintf('%%%02X', ord($string[$j])), $j, 1);
					$j += 2;
					$position += 2;
					$strlen += 2;
				}
			}
		}

		return $string;
	}