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Re: Functions behaving badly: PHP str_split on an empty string

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On 17/02/2016 10:53, Christoph M. Becker wrote:
> James Harris wrote:

...

>> Is there a recommended way to iterate over the characters of a string
>> when that string could be single-byte ASCII or multi-byte Unicode?
>
> You can use mb_split() or preg_split() for multibyte character
> encodings.  Anyway, you should be aware in which character encoding the
> string is encoded (mb_detect_encoding() might be helpful).

That was useful in making it possible for me to check the types of 
strings. Given:

$request_uri = $_SERVER["REQUEST_URI"];
$uri = urldecode($request_uri)

On this server (Apache) $request_uri is ASCII, even if the URL had some 
Chinese characters in it.

As for $uri, if the input is just ASCII characters then $uri (the output 
of urldecode) is plain ASCII. But if the input contains Chinese 
characters then $uri will be Unicode.

I presume my choices are essentially either to report non-ASCII 
characters as errors or to do all processing in Unicode.

> However, I suggest you reconsider the approach to iterate over the
> characters of a string, because it's most likely rather slow in PHP (for
> one, PHP doesn't have a char type as C does, so a character is stored as
> string[2]), and there may be better alternatives available (PCRE comes
> to mind).

There may be a better way to do it. Here is some of my current code

$request_uri = trim(urldecode($_SERVER["REQUEST_URI"]), "/");
foreach (str_split($request_uri) as $char) {
   if (strpos($path_chars_permitted, $char) === false) {
     $etext .= " Invalid character in URL: \"" .
        htmlspecialchars($char) . "\"<br/>\n";
   }
}

Suggestions for improvement welcome. Maybe there is a function to do the 
lot in one go that would save me iterating over the string. I think the 
best thing would be to convert the above to handle Unicode. That would 
allow better error messages.

(I now know that str_split won't work when $request_uri is empty.)

James

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Thread

Functions behaving badly: PHP str_split on an empty string James Harris <james.harris.1@gmail.com> - 2016-02-17 09:57 +0000
  Re: Functions behaving badly: PHP str_split on an empty string "Christoph M. Becker" <cmbecker69@arcor.de> - 2016-02-17 11:53 +0100
    Re: Functions behaving badly: PHP str_split on an empty string James Harris <james.harris.1@gmail.com> - 2016-02-17 16:04 +0000
      Re: Functions behaving badly: PHP str_split on an empty string Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-17 23:12 +0100

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