diff --git a/src/utils/utf8.php b/src/utils/utf8.php
index f03663f3..c92ee533 100644
--- a/src/utils/utf8.php
+++ b/src/utils/utf8.php
@@ -1,982 +1,984 @@
 <?php
 
 /**
  * Convert a string into valid UTF-8. This function is quite slow.
  *
  * When invalid byte subsequences are encountered, they will be replaced with
  * U+FFFD, the Unicode replacement character.
  *
  * This function treats overlong encodings as invalid.
  *
  * @param   string  String to convert to valid UTF-8.
  * @return  string  String with invalid UTF-8 byte subsequences replaced with
  *                  U+FFFD.
  */
 function phutil_utf8ize($string) {
   if (phutil_is_utf8($string)) {
     return $string;
   }
 
   // There is no function to do this in iconv, mbstring or ICU to do this, so
   // do it (very very slowly) in pure PHP.
 
   // TODO: Provide an optional fast C implementation ala fb_utf8ize() if this
   // ever shows up in profiles?
 
   $result = array();
 
   $regex =
     "/([\x01-\x7F]".
       "|[\xC2-\xDF][\x80-\xBF]".
       "|[\xE0][\xA0-\xBF][\x80-\xBF]".
       "|[\xE1-\xEF][\x80-\xBF][\x80-\xBF]".
       "|[\xF0][\x90-\xBF][\x80-\xBF][\x80-\xBF]".
       "|[\xF1-\xF3][\x80-\xBF][\x80-\xBF][\x80-\xBF]".
       "|[\xF4][\x80-\x8F][\x80-\xBF][\x80-\xBF])".
     "|(.)/";
 
   $replacement = "\xEF\xBF\xBD";
 
   $offset = 0;
   $matches = null;
   while (preg_match($regex, $string, $matches, 0, $offset)) {
     if (!isset($matches[2])) {
       $match = $matches[1];
 
       if ($match[0] == "\xED") {
         // If this is a 3-byte character that may be part of one of the
         // surrogate ranges, check if it's actually in those ranges. Reject
         // it as invalid if it is. These sequences are used in UTF16 and
         // functions like json_encode() refuse to encode them.
 
         $codepoint = ((ord($match[0]) & 0x0F) << 12)
                    + ((ord($match[1]) & 0x3F) << 6)
                    + ((ord($match[2]) & 0x3F));
         if ($codepoint >= 0xD800 && $codepoint <= 0xDFFF) {
           $result[] = str_repeat($replacement, strlen($match));
           $offset += strlen($matches[0]);
           continue;
         }
       }
 
       $result[] = $match;
     } else {
       // Unicode replacement character, U+FFFD.
       $result[] = $replacement;
     }
 
     $offset += strlen($matches[0]);
   }
 
   return implode('', $result);
 }
 
 
 /**
  * Determine if a string is valid UTF-8, with only basic multilingual plane
  * characters. This is particularly important because MySQL's `utf8` column
  * types silently truncate strings which contain characters outside of this
  * set.
  *
  * @param string  String to test for being valid UTF-8 with only characters in
  *                the basic multilingual plane.
  * @return bool   True if the string is valid UTF-8 with only BMP characters.
  */
 function phutil_is_utf8_with_only_bmp_characters($string) {
   return phutil_is_utf8_slowly($string, $only_bmp = true);
 }
 
 
 /**
  * Determine if a string is valid UTF-8.
  *
  * @param string  Some string which may or may not be valid UTF-8.
  * @return bool    True if the string is valid UTF-8.
  */
 function phutil_is_utf8($string) {
   if (function_exists('mb_check_encoding')) {
     // See T13527. In some versions of PHP, "mb_check_encoding()" strictly
     // requires a string parameter.
     $string = phutil_string_cast($string);
 
     // If mbstring is available, this is significantly faster than using PHP.
     return mb_check_encoding($string, 'UTF-8');
   }
 
   return phutil_is_utf8_slowly($string);
 }
 
 
 /**
  * Determine if a string is valid UTF-8, slowly.
  *
  * This works on any system, but has very poor performance.
  *
  * You should call @{function:phutil_is_utf8} instead of this function, as
  * that function can use more performant mechanisms if they are available on
  * the system.
  *
  * @param string  Some string which may or may not be valid UTF-8.
  * @param bool    True to require all characters be part of the basic
  *                multilingual plane (no more than 3-bytes long).
  * @return bool   True if the string is valid UTF-8.
  */
 function phutil_is_utf8_slowly($string, $only_bmp = false) {
   // First, check the common case of normal ASCII strings. We're fine if
   // the string contains no bytes larger than 127.
   if (preg_match('/^[\x01-\x7F]+\z/', $string)) {
     return true;
   }
 
   // NOTE: In the past, we used a large regular expression in the form of
   // '(x|y|z)+' to match UTF8 strings. However, PCRE can segfaults on patterns
   // like this at relatively small input sizes, at least on some systems
   // (observed on OSX and Windows). This is apparently because the internal
   // implementation is recursive and it blows the stack.
 
   // See <https://bugs.php.net/bug.php?id=45735> for some discussion. Since the
   // input limit is extremely low (less than 50KB on my system), do this check
   // very very slowly in PHP instead. See also T5316.
 
   $len = strlen($string);
   for ($ii = 0; $ii < $len; $ii++) {
     $chr = ord($string[$ii]);
     if ($chr >= 0x01 && $chr <= 0x7F) {
       continue;
     } else if ($chr >= 0xC2 && $chr <= 0xDF) {
       ++$ii;
       if ($ii >= $len) {
         return false;
       }
       $chr = ord($string[$ii]);
       if ($chr >= 0x80 && $chr <= 0xBF) {
         continue;
       }
       return false;
     } else if ($chr == 0xED) {
       // See T11525. Some sequences in this block are surrogate codepoints
       // that are reserved for use in UTF16. We should reject them.
       $codepoint = ($chr & 0x0F) << 12;
       ++$ii;
       if ($ii >= $len) {
         return false;
       }
       $chr = ord($string[$ii]);
       $codepoint += ($chr & 0x3F) << 6;
       if ($chr >= 0x80 && $chr <= 0xBF) {
         ++$ii;
         if ($ii >= $len) {
           return false;
         }
         $chr = ord($string[$ii]);
         $codepoint += ($chr & 0x3F);
 
         if ($codepoint >= 0xD800 && $codepoint <= 0xDFFF) {
           // Reject these surrogate codepoints.
           return false;
         }
 
         if ($chr >= 0x80 && $chr <= 0xBF) {
           continue;
         }
       }
       return false;
     } else if ($chr > 0xE0 && $chr <= 0xEF) {
       ++$ii;
       if ($ii >= $len) {
         return false;
       }
       $chr = ord($string[$ii]);
       if ($chr >= 0x80 && $chr <= 0xBF) {
         ++$ii;
         if ($ii >= $len) {
           return false;
         }
         $chr = ord($string[$ii]);
         if ($chr >= 0x80 && $chr <= 0xBF) {
           continue;
         }
       }
       return false;
     } else if ($chr == 0xE0) {
       ++$ii;
       if ($ii >= $len) {
         return false;
       }
       $chr = ord($string[$ii]);
 
       // NOTE: This range starts at 0xA0, not 0x80. The values 0x80-0xA0 are
       // "valid", but not minimal representations, and MySQL rejects them. We're
       // special casing this part of the range.
 
       if ($chr >= 0xA0 && $chr <= 0xBF) {
         ++$ii;
         if ($ii >= $len) {
           return false;
         }
         $chr = ord($string[$ii]);
         if ($chr >= 0x80 && $chr <= 0xBF) {
           continue;
         }
       }
       return false;
     } else if (!$only_bmp) {
       if ($chr > 0xF0 && $chr <= 0xF4) {
         ++$ii;
         if ($ii >= $len) {
           return false;
         }
         $chr = ord($string[$ii]);
         if ($chr >= 0x80 && $chr <= 0xBF) {
           ++$ii;
           if ($ii >= $len) {
             return false;
           }
           $chr = ord($string[$ii]);
           if ($chr >= 0x80 && $chr <= 0xBF) {
             ++$ii;
             if ($ii >= $len) {
               return false;
             }
             $chr = ord($string[$ii]);
             if ($chr >= 0x80 && $chr <= 0xBF) {
               continue;
             }
           }
         }
       } else if ($chr == 0xF0) {
         ++$ii;
         if ($ii >= $len) {
           return false;
         }
         $chr = ord($string[$ii]);
 
         // NOTE: As above, this range starts at 0x90, not 0x80. The values
         // 0x80-0x90 are not minimal representations.
 
         if ($chr >= 0x90 && $chr <= 0xBF) {
           ++$ii;
           if ($ii >= $len) {
             return false;
           }
           $chr = ord($string[$ii]);
           if ($chr >= 0x80 && $chr <= 0xBF) {
             ++$ii;
             if ($ii >= $len) {
               return false;
             }
             $chr = ord($string[$ii]);
             if ($chr >= 0x80 && $chr <= 0xBF) {
               continue;
             }
           }
         }
       }
     }
 
     return false;
   }
 
   return true;
 }
 
 
 /**
  * Find the character length of a UTF-8 string.
  *
  * @param string A valid utf-8 string.
  * @return int   The character length of the string.
  */
 function phutil_utf8_strlen($string) {
   if (function_exists('utf8_decode')) {
     return strlen(utf8_decode($string));
   }
   return count(phutil_utf8v($string));
 }
 
 
 /**
  * Find the console display length of a UTF-8 string. This may differ from the
  * character length of the string if it contains double-width characters, like
  * many Chinese characters.
  *
  * This method is based on a C implementation here, which is based on the IEEE
  * standards. The source has more discussion and addresses more considerations
  * than this implementation does.
  *
  *   http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
  *
  * NOTE: We currently assume width 1 for East-Asian ambiguous characters.
  *
  * NOTE: This function is VERY slow.
  *
  * @param   string  A valid UTF-8 string.
  * @return  int     The console display length of the string.
  */
 function phutil_utf8_console_strlen($string) {
   // Formatting and colors don't contribute any width in the console.
   $string = preg_replace("/\x1B\[\d*m/", '', $string);
 
   // In the common case of an ASCII string, just return the string length.
   if (preg_match('/^[\x01-\x7F]*\z/', $string)) {
     return strlen($string);
   }
 
   $len = 0;
 
   // NOTE: To deal with combining characters, we're splitting the string into
   // glyphs first (characters with combiners) and then counting just the width
   // of the first character in each glyph.
 
   $display_glyphs = phutil_utf8v_combined($string);
   foreach ($display_glyphs as $display_glyph) {
     $glyph_codepoints = phutil_utf8v_codepoints($display_glyph);
     foreach ($glyph_codepoints as $c) {
       if ($c == 0) {
         break;
       }
 
       $len += 1 +
         ($c >= 0x1100 &&
           ($c <= 0x115F ||                    /* Hangul Jamo init. consonants */
             $c == 0x2329 || $c == 0x232A ||
             ($c >= 0x2E80 && $c <= 0xA4CF &&
               $c != 0x303F) ||                  /* CJK ... Yi */
             ($c >= 0xAC00 && $c <= 0xD7A3) || /* Hangul Syllables */
             ($c >= 0xF900 && $c <= 0xFAFF) || /* CJK Compatibility Ideographs */
             ($c >= 0xFE10 && $c <= 0xFE19) || /* Vertical forms */
             ($c >= 0xFE30 && $c <= 0xFE6F) || /* CJK Compatibility Forms */
             ($c >= 0xFF00 && $c <= 0xFF60) || /* Fullwidth Forms */
             ($c >= 0xFFE0 && $c <= 0xFFE6) ||
             ($c >= 0x20000 && $c <= 0x2FFFD) ||
             ($c >= 0x30000 && $c <= 0x3FFFD)));
 
       break;
     }
   }
 
   return $len;
 }
 
 
 /**
  * Test if a string contains Chinese, Japanese, or Korean characters.
  *
  * Most languages use spaces to separate words, but these languages do not.
  *
  * @param string String to examine, in UTF8.
  * @return bool True if the string contains Chinese, Japanese, or Korean
  *   characters.
  */
 function phutil_utf8_is_cjk($string) {
   $codepoints = phutil_utf8v_codepoints($string);
 
   foreach ($codepoints as $codepoint) {
     // CJK Unified Ideographs
     if ($codepoint >= 0x4E00 && $codepoint <= 0x9FFF) {
       return true;
     }
 
     // CJK Unified Ideographs Extension A
     if ($codepoint >= 0x3400 && $codepoint <= 0x4DBF) {
       return true;
     }
 
     // CJK Unified Ideographs Extension B
     if ($codepoint >= 0x20000 && $codepoint <= 0x2A6DF) {
       return true;
     }
 
     // CJK Unified Ideographs Extension C
     if ($codepoint >= 0x2A700 && $codepoint <= 0x2B73F) {
       return true;
     }
 
     // CJK Unified Ideographs Extension D
     if ($codepoint >= 0x2B740 && $codepoint <= 0x2B81F) {
       return true;
     }
 
     // CJK Unified Ideographs Extension E
     if ($codepoint >= 0x2B820 && $codepoint <= 0x2CEAF) {
       return true;
     }
 
     // CJK Unified Ideographs Extension F
     if ($codepoint >= 0x2CEB0 && $codepoint <= 0x2EBEF) {
       return true;
     }
 
     // CJK Compatibility Ideographs
     if ($codepoint >= 0xF900 && $codepoint <= 0xFAFF) {
       return true;
     }
   }
 
   return false;
 }
 
 
 /**
  * Split a UTF-8 string into an array of characters. Combining characters are
  * also split.
  *
  * @param string A valid utf-8 string.
  * @param int|null Stop processing after examining this many bytes.
  * @return list  A list of characters in the string.
  */
 function phutil_utf8v($string, $byte_limit = null) {
+  $string = phutil_string_cast($string);
+
   $res = array();
   $len = strlen($string);
 
   $ii = 0;
   while ($ii < $len) {
     $byte = $string[$ii];
     if ($byte <= "\x7F") {
       $res[] = $byte;
       $ii += 1;
 
       if ($byte_limit && ($ii >= $byte_limit)) {
         break;
       }
 
       continue;
     } else if ($byte < "\xC0") {
       throw new Exception(
         pht('Invalid UTF-8 string passed to %s.', __FUNCTION__));
     } else if ($byte <= "\xDF") {
       $seq_len = 2;
     } else if ($byte <= "\xEF") {
       $seq_len = 3;
     } else if ($byte <= "\xF7") {
       $seq_len = 4;
     } else if ($byte <= "\xFB") {
       $seq_len = 5;
     } else if ($byte <= "\xFD") {
       $seq_len = 6;
     } else {
       throw new Exception(
         pht('Invalid UTF-8 string passed to %s.', __FUNCTION__));
     }
 
     if ($ii + $seq_len > $len) {
       throw new Exception(
         pht('Invalid UTF-8 string passed to %s.', __FUNCTION__));
     }
     for ($jj = 1; $jj < $seq_len; ++$jj) {
       if ($string[$ii + $jj] >= "\xC0") {
         throw new Exception(
           pht('Invalid UTF-8 string passed to %s.', __FUNCTION__));
       }
     }
     $res[] = substr($string, $ii, $seq_len);
     $ii += $seq_len;
 
     if ($byte_limit && ($ii >= $byte_limit)) {
       break;
     }
   }
 
   return $res;
 }
 
 
 /**
  * Split a UTF-8 string into an array of codepoints (as integers).
  *
  * @param   string  A valid UTF-8 string.
  * @return  list    A list of codepoints, as integers.
  */
 function phutil_utf8v_codepoints($string) {
   $str_v = phutil_utf8v($string);
 
   foreach ($str_v as $key => $char) {
     $c = ord($char[0]);
     $v = 0;
 
     if (($c & 0x80) == 0) {
       $v = $c;
     } else if (($c & 0xE0) == 0xC0) {
       $v = (($c & 0x1F) << 6)
          + ((ord($char[1]) & 0x3F));
     } else if (($c & 0xF0) == 0xE0) {
       $v = (($c & 0x0F) << 12)
          + ((ord($char[1]) & 0x3F) << 6)
          + ((ord($char[2]) & 0x3F));
     } else if (($c & 0xF8) == 0xF0) {
       $v = (($c & 0x07) << 18)
          + ((ord($char[1]) & 0x3F) << 12)
          + ((ord($char[2]) & 0x3F) << 6)
          + ((ord($char[3]) & 0x3F));
     } else if (($c & 0xFC) == 0xF8) {
       $v = (($c & 0x03) << 24)
          + ((ord($char[1]) & 0x3F) << 18)
          + ((ord($char[2]) & 0x3F) << 12)
          + ((ord($char[3]) & 0x3F) << 6)
          + ((ord($char[4]) & 0x3F));
     } else if (($c & 0xFE) == 0xFC) {
       $v = (($c & 0x01) << 30)
          + ((ord($char[1]) & 0x3F) << 24)
          + ((ord($char[2]) & 0x3F) << 18)
          + ((ord($char[3]) & 0x3F) << 12)
          + ((ord($char[4]) & 0x3F) << 6)
          + ((ord($char[5]) & 0x3F));
     }
 
     $str_v[$key] = $v;
   }
 
   return $str_v;
 }
 
 
 /**
  * Convert a Unicode codepoint into a UTF8-encoded string.
  *
  * @param int Unicode codepoint.
  * @return string UTF8 encoding.
  */
 function phutil_utf8_encode_codepoint($codepoint) {
   if ($codepoint < 0x80) {
     $r = chr($codepoint);
   } else if ($codepoint < 0x800) {
     $r = chr(0xC0 | (($codepoint >> 6)  & 0x1F)).
          chr(0x80 | (($codepoint)       & 0x3F));
   } else if ($codepoint < 0x10000) {
     $r = chr(0xE0 | (($codepoint >> 12) & 0x0F)).
          chr(0x80 | (($codepoint >> 6)  & 0x3F)).
          chr(0x80 | (($codepoint)       & 0x3F));
   } else if ($codepoint < 0x110000) {
     $r = chr(0xF0 | (($codepoint >> 18) & 0x07)).
          chr(0x80 | (($codepoint >> 12) & 0x3F)).
          chr(0x80 | (($codepoint >> 6)  & 0x3F)).
          chr(0x80 | (($codepoint)       & 0x3F));
   } else {
     throw new Exception(
       pht(
         'Encoding UTF8 codepoint "%s" is not supported.',
         $codepoint));
   }
 
   return $r;
 }
 
 
 /**
  * Hard-wrap a block of UTF-8 text with embedded HTML tags and entities.
  *
  * @param   string An HTML string with tags and entities.
  * @return  list   List of hard-wrapped lines.
  */
 function phutil_utf8_hard_wrap_html($string, $width) {
   $break_here = array();
 
   // Convert the UTF-8 string into a list of UTF-8 characters.
   $vector = phutil_utf8v($string);
   $len = count($vector);
   $char_pos = 0;
   for ($ii = 0; $ii < $len; ++$ii) {
     // An ampersand indicates an HTML entity; consume the whole thing (until
     // ";") but treat it all as one character.
     if ($vector[$ii] == '&') {
       do {
         ++$ii;
       } while ($vector[$ii] != ';');
       ++$char_pos;
     // An "<" indicates an HTML tag, consume the whole thing but don't treat
     // it as a character.
     } else if ($vector[$ii] == '<') {
       do {
         ++$ii;
       } while ($vector[$ii] != '>');
     } else {
       ++$char_pos;
     }
 
     // Keep track of where we need to break the string later.
     if ($char_pos == $width) {
       $break_here[$ii] = true;
       $char_pos = 0;
     }
   }
 
   $result = array();
   $string = '';
   foreach ($vector as $ii => $char) {
     $string .= $char;
     if (isset($break_here[$ii])) {
       $result[] = $string;
       $string = '';
     }
   }
 
   if (strlen($string)) {
     $result[] = $string;
   }
 
   return $result;
 }
 
 /**
   * Hard-wrap a block of UTF-8 text with no embedded HTML tags and entities.
   *
   * @param string A non HTML string
   * @param int Width of the hard-wrapped lines
   * @return list List of hard-wrapped lines.
   */
 function phutil_utf8_hard_wrap($string, $width) {
   $result = array();
 
   $lines = phutil_split_lines($string, $retain_endings = false);
   foreach ($lines as $line) {
 
     // Convert the UTF-8 string into a list of UTF-8 characters.
     $vector = phutil_utf8v($line);
 
     $len = count($vector);
     $buffer = '';
 
     for ($ii = 1; $ii <= $len; ++$ii) {
       $buffer .= $vector[$ii - 1];
       if (($ii % $width) === 0) {
         $result[] = $buffer;
         $buffer = '';
       }
     }
 
     if (strlen($buffer)) {
       $result[] = $buffer;
     }
   }
 
   return $result;
 }
 
 /**
  * Convert a string from one encoding (like ISO-8859-1) to another encoding
  * (like UTF-8).
  *
  * This is primarily a thin wrapper around `mb_convert_encoding()` which checks
  * you have the extension installed, since we try to require the extension
  * only if you actually need it (i.e., you want to work with encodings other
  * than UTF-8).
  *
  * NOTE: This function assumes that the input is in the given source encoding.
  * If it is not, it may not output in the specified target encoding. If you
  * need to perform a hard conversion to UTF-8, use this function in conjunction
  * with @{function:phutil_utf8ize}. We can detect failures caused by invalid
  * encoding names, but `mb_convert_encoding()` fails silently if the
  * encoding name identifies a real encoding but the string is not actually
  * encoded with that encoding.
  *
  * @param string String to re-encode.
  * @param string Target encoding name, like "UTF-8".
  * @param string Source encoding name, like "ISO-8859-1".
  * @return string Input string, with converted character encoding.
  *
  * @phutil-external-symbol function mb_convert_encoding
  */
 function phutil_utf8_convert($string, $to_encoding, $from_encoding) {
   if (!$from_encoding) {
     throw new InvalidArgumentException(
       pht(
         'Attempting to convert a string encoding, but no source encoding '.
         'was provided. Explicitly provide the source encoding.'));
   }
   if (!$to_encoding) {
     throw new InvalidArgumentException(
       pht(
         'Attempting to convert a string encoding, but no target encoding '.
         'was provided. Explicitly provide the target encoding.'));
   }
 
   // Normalize encoding names so we can no-op the very common case of UTF8
   // to UTF8 (or any other conversion where both encodings are identical).
   $to_upper = strtoupper(str_replace('-', '', $to_encoding));
   $from_upper = strtoupper(str_replace('-', '', $from_encoding));
   if ($from_upper == $to_upper) {
     return $string;
   }
 
   if (!function_exists('mb_convert_encoding')) {
     throw new Exception(
       pht(
         "Attempting to convert a string encoding from '%s' to '%s', ".
         "but the '%s' PHP extension is not available. Install %s to ".
         "work with encodings other than UTF-8.",
         $from_encoding,
         $to_encoding,
         'mbstring',
         'mbstring'));
   }
 
   $result = @mb_convert_encoding($string, $to_encoding, $from_encoding);
 
   if ($result === false) {
     $message = error_get_last();
     if ($message) {
       $message = idx($message, 'message', pht('Unknown error.'));
     }
     throw new Exception(
       pht(
         "String conversion from encoding '%s' to encoding '%s' failed: %s",
         $from_encoding,
         $to_encoding,
         $message));
   }
 
   return $result;
 }
 
 
 /**
  * Convert a string to title case in a UTF8-aware way. This function doesn't
  * necessarily do a great job, but the builtin implementation of `ucwords()` can
  * completely destroy inputs, so it just has to be better than that. Similar to
  * @{function:ucwords}.
  *
  * @param   string  UTF-8 input string.
  * @return  string  Input, in some semblance of title case.
  */
 function phutil_utf8_ucwords($str) {
   // NOTE: mb_convert_case() discards uppercase letters in words when converting
   // to title case. For example, it will convert "AAA" into "Aaa", which is
   // undesirable.
 
   $v = phutil_utf8v($str);
   $result = '';
   $last = null;
 
   $ord_a = ord('a');
   $ord_z = ord('z');
   foreach ($v as $c) {
     $convert = false;
     if ($last === null || $last === ' ') {
       $o = ord($c[0]);
       if ($o >= $ord_a && $o <= $ord_z) {
         $convert = true;
       }
     }
 
     if ($convert) {
       $result .= phutil_utf8_strtoupper($c);
     } else {
       $result .= $c;
     }
 
     $last = $c;
   }
 
   return $result;
 }
 
 
 /**
  * Convert a string to lower case in a UTF8-aware way. Similar to
  * @{function:strtolower}.
  *
  * @param   string  UTF-8 input string.
  * @return  string  Input, in some semblance of lower case.
  *
  * @phutil-external-symbol function mb_convert_case
  */
 function phutil_utf8_strtolower($str) {
   if (function_exists('mb_convert_case')) {
     return mb_convert_case($str, MB_CASE_LOWER, 'UTF-8');
   }
 
   static $map;
   if ($map === null) {
     $map = array_combine(
       range('A', 'Z'),
       range('a', 'z'));
   }
 
   return phutil_utf8_strtr($str, $map);
 }
 
 
 /**
  * Convert a string to upper case in a UTF8-aware way. Similar to
  * @{function:strtoupper}.
  *
  * @param   string  UTF-8 input string.
  * @return  string  Input, in some semblance of upper case.
  *
  * @phutil-external-symbol function mb_convert_case
  */
 function phutil_utf8_strtoupper($str) {
   if (function_exists('mb_convert_case')) {
     return mb_convert_case($str, MB_CASE_UPPER, 'UTF-8');
   }
 
   static $map;
   if ($map === null) {
     $map = array_combine(
       range('a', 'z'),
       range('A', 'Z'));
   }
 
   return phutil_utf8_strtr($str, $map);
 }
 
 
 /**
  * Replace characters in a string in a UTF-aware way. Similar to
  * @{function:strtr}.
  *
  * @param   string              UTF-8 input string.
  * @param   map<string, string> Map of characters to replace.
  * @return  string              Input with translated characters.
  */
 function phutil_utf8_strtr($str, array $map) {
   $v = phutil_utf8v($str);
   $result = '';
   foreach ($v as $c) {
     if (isset($map[$c])) {
       $result .= $map[$c];
     } else {
       $result .= $c;
     }
   }
 
   return $result;
 }
 
 /**
  * Determine if a given unicode character is a combining character or not.
  *
  * @param   string              A single unicode character.
  * @return  boolean             True or false.
  */
 function phutil_utf8_is_combining_character($character) {
   $components = phutil_utf8v_codepoints($character);
 
   // Combining Diacritical Marks (0300 - 036F).
   // Combining Diacritical Marks Supplement (1DC0 - 1DFF).
   // Combining Diacritical Marks for Symbols (20D0 - 20FF).
   // Combining Half Marks (FE20 - FE2F).
 
   foreach ($components as $codepoint) {
     if ($codepoint >= 0x0300 && $codepoint <= 0x036F ||
          $codepoint >= 0x1DC0 && $codepoint <= 0x1DFF ||
          $codepoint >= 0x20D0 && $codepoint <= 0x20FF ||
          $codepoint >= 0xFE20 && $codepoint <= 0xFE2F) {
       return true;
     }
   }
 
   return false;
 }
 
 
 /**
  * Split a UTF-8 string into an array of characters. Combining characters
  * are not split.
  *
  * @param string A valid utf-8 string.
  * @return list  A list of characters in the string.
  */
 function phutil_utf8v_combined($string) {
   $components = phutil_utf8v($string);
   return phutil_utf8v_combine_characters($components);
 }
 
 
 /**
  * Merge combining characters in a UTF-8 string.
  *
  * This is a low-level method which can allow other operations to do less work.
  * If you have a string, call @{method:phutil_utf8v_combined} instead.
  *
  * @param list List of UTF-8 characters.
  * @return list List of UTF-8 strings with combining characters merged.
  */
 function phutil_utf8v_combine_characters(array $characters) {
   if (!$characters) {
     return array();
   }
 
   // If the first character in the string is a combining character,
   // start with a space.
   if (phutil_utf8_is_combining_character($characters[0])) {
     $buf = ' ';
   } else {
     $buf = null;
   }
 
   $parts = array();
   foreach ($characters as $character) {
     if (!isset($character[1])) {
       // This an optimization: there are no one-byte combining characters,
       // so we can just pass these through unmodified.
       $is_combining = false;
     } else {
       $is_combining = phutil_utf8_is_combining_character($character);
     }
 
     if ($is_combining) {
       $buf .= $character;
     } else {
       if ($buf !== null) {
         $parts[] = $buf;
       }
       $buf = $character;
     }
   }
 
   $parts[] = $buf;
 
   return $parts;
 }
 
 
 /**
  * Return the current system locale setting (LC_ALL).
  *
  * @return string Current system locale setting.
  */
 function phutil_get_system_locale() {
   $locale = setlocale(LC_ALL, 0);
 
   if ($locale === false) {
     throw new Exception(
       pht(
         'Unable to determine current system locale (call to '.
         '"setlocale(LC_ALL, 0)" failed).'));
   }
 
   return $locale;
 }
 
 
 /**
  * Test if a system locale (LC_ALL) is available on the system.
  *
  * @param string Locale name like "en_US.UTF-8".
  * @return bool True if the locale is available.
  */
 function phutil_is_system_locale_available($locale) {
   $old_locale = phutil_get_system_locale();
   $is_available = @setlocale(LC_ALL, $locale);
   setlocale(LC_ALL, $old_locale);
 
   return ($is_available !== false);
 }
 
 
 /**
  * Set the system locale (LC_ALL) to a particular value.
  *
  * @param string New locale setting.
  * @return void
  */
 function phutil_set_system_locale($locale) {
   $ok = @setlocale(LC_ALL, $locale);
   if (!$ok) {
     throw new Exception(
       pht(
         'Failed to set system locale (to "%s").',
         $locale));
   }
 }