Php function UTF-8 characters issue - php

Question

Here is my function that makes the first character of the first word of a sentence uppercase:
function sentenceCase($str)
{
$cap = true;
$ret = '';
for ($x = 0; $x < strlen($str); $x++) {
$letter = substr($str, $x, 1);
if ($letter == "." || $letter == "!" || $letter == "?") {
$cap = true;
} elseif ($letter != " " && $cap == true) {
$letter = strtoupper($letter);
$cap = false;
}
$ret .= $letter;
}
return $ret;
}
It converts "sample sentence" into "Sample sentence". The problem is, it doesn't capitalize UTF-8 characters. See this example.
What am I doing wrong?

Answer 1

The most straightforward way to make your code UTF-8 aware is to use mbstring functions instead of the plain dumb ones in the three cases where the latter appear:
function sentenceCase($str)
{
$cap = true;
$ret = '';
for ($x = 0; $x < mb_strlen($str); $x++) { // mb_strlen instead
$letter = mb_substr($str, $x, 1); // mb_substr instead
if ($letter == "." || $letter == "!" || $letter == "?") {
$cap = true;
} elseif ($letter != " " && $cap == true) {
$letter = mb_strtoupper($letter); // mb_strtoupper instead
$cap = false;
}
$ret .= $letter;
}
return $ret;
}
You can then configure mbstring to work with UTF-8 strings and you are ready to go:
mb_internal_encoding('UTF-8');
echo sentenceCase ("üias skdfnsknka");
Bonus solution
Specifically for UTF-8 you can also use a regular expression, which will result in less code:
$str = "üias skdfnsknka";
echo preg_replace_callback(
'/((?:^|[!.?])\s*)(\p{Ll})/u',
function($match) { return $match[1].mb_strtoupper($match[2], 'UTF-8'); },
$str);