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Convert UTF-8 encoded string to Unicode entities

Takes a string of utf-8 encoded characters and converts it to a string of unicode entities. Each unicode entitiy has the form &#nnnnn; or &#nnn; n={0..9} and can be displayed by utf-8 supporting browsers. If the character passed maps as lower ascii it stays as such (a single char) instead of being presented as a unicode entity

Info

Source Code ( 88 lines )

/**
* takes a string of utf-8 encoded characters and converts it to a string of unicode entities
* each unicode entitiy has the either the form &#nnnnn; or &#nnn; n={0..9} and can be displayed by utf-8 supporting
* browsers.
* If the character passed maps as lower ascii it stays as such (a single char) instead of being presented as a unicode entity
* @author Ronen Botzer
* @param $source string encoded using utf-8 [STRING]
* @return string of unicode entities [STRING]
* @access public
*/
function utf8ToUnicodeEntities ($source) {
	// array used to figure what number to decrement from character order value 
	// according to number of characters used to map unicode to ascii by utf-8
	$decrement[4] = 240;
	$decrement[3] = 224;
	$decrement[2] = 192;
	$decrement[1] = 0;
	
	// the number of bits to shift each charNum by
	$shift[1][0] = 0;
	$shift[2][0] = 6;
	$shift[2][1] = 0;
	$shift[3][0] = 12;
	$shift[3][1] = 6;
	$shift[3][2] = 0;
	$shift[4][0] = 18;
	$shift[4][1] = 12;
	$shift[4][2] = 6;
	$shift[4][3] = 0;
	
	$pos = 0;
	$len = strlen ($source);
	$encodedString = '';
	while ($pos < $len) {
		$asciiPos = ord (substr ($source, $pos, 1));
		if (($asciiPos >= 240) && ($asciiPos <= 255)) {
			// 4 chars representing one unicode character
			$thisLetter = substr ($source, $pos, 4);
			$pos += 4;
		}
		else if (($asciiPos >= 224) && ($asciiPos <= 239)) {
			// 3 chars representing one unicode character
			$thisLetter = substr ($source, $pos, 3);
			$pos += 3;
		}
		else if (($asciiPos >= 192) && ($asciiPos <= 223)) {
			// 2 chars representing one unicode character
			$thisLetter = substr ($source, $pos, 2);
			$pos += 2;
		}
		else {
			// 1 char (lower ascii)
			$thisLetter = substr ($source, $pos, 1);
			$pos += 1;
		}

		$thisLen = strlen ($thisLetter);
		if ($thisLen > 1) {
			// process the string representing the letter to a unicode entity
			$thisPos = 0;
			$decimalCode = 0;
			while ($thisPos < $thisLen) {
				$thisCharOrd = ord (substr ($thisLetter, $thisPos, 1));
				if ($thisPos == 0) {
					$charNum = intval ($thisCharOrd - $decrement[$thisLen]);
					$decimalCode += ($charNum << $shift[$thisLen][$thisPos]);
				}
				else {
					$charNum = intval ($thisCharOrd - 128);
					$decimalCode += ($charNum << $shift[$thisLen][$thisPos]);
				}

				$thisPos++;
			}

			if ($thisLen == 1)
				$encodedLetter = "&#". str_pad($decimalCode, 3, "0", STR_PAD_LEFT) . ';';
			else
				$encodedLetter = "&#". str_pad($decimalCode, 5, "0", STR_PAD_LEFT) . ';';

			$encodedString .= $encodedLetter;
		}
		else {
			$encodedString .= $thisLetter;
		}
	}
	return $encodedString;
}