How to convert hex codes in JSON data using PHP

Question

I have some content that is generated by the Drupal CMS that contains strings like:

\"... \\n Proficient knowledge of \\x3cstrong\\x3emedical\\x3c/strong\\x3         


        

Answer 1

Ok, this will do it:

/**
 * Converts all UTF-8 Units ( \xXX ) back into ascii characters.  
 * 
 * @param string $input   String which includes some UTF-8 units
 * @return string
 */
function convertUTF8Units($input) {
    include $path;
    $part = "";
    $output = $input;
    $len = strlen($input)-4;

    for($i=0; $i<=$len; $i++) {
      $part = substr($input, $i, 4);

      if ((substr($part, 0, 2) === "\\x")) {          
        $raw = hex2bin( $part );
        $raw = trim($raw);
        $pattern = "/\\".$part."/";
        $output = preg_replace($pattern, $raw, $output);
      }

    }
    return $output;
}

/**
 * Function to convert a hex code back to ascii string.  Taken from 
 * http://devcorner.georgievi.net/pages/programming/php/hex2bin-php.
 * 
 * @param string $hex_string   String of format: \xXX
 * @return string
 */
define('HEX2BIN_WS', " \t\n\r");
function hex2bin($hex_string) {
  $pos = 0;
    $result = '';
    while ($pos < strlen($hex_string)) {
      if (strpos(HEX2BIN_WS, $hex_string{$pos}) !== FALSE) {
        $pos++;
      } 
    else {
        $code = hexdec(substr($hex_string, $pos, 2));
      $pos = $pos + 2;
        $result .= chr($code); 
      }
    }
    return $result;
}

I'm a little fuzzy on exactly what I'm converting to what though; all I'm sure about is that it passes all the JSON validators now. While pursuing this UTF-8, UTF-8 Units, Binary somethings, Hex values and ascii characters have all come up. I can't actually articulate the difference, nor can I definitively say what the input, conversions, or output of these functions are.

Can anyone walk me through what my code is doing? :P