Textarea值长度

Question

I'm trying to limit the number of entered unicode characters in a textarea to 500.
When I try to post the form and get the textarea content to check its length in the back-end, I get a double length, meaning the value I get from strlen is twice the number of the inputted characters.

What is the problem here?

<textarea id="ArticleSummary" name="ArticleSummary" rows="4" maxlength="500">
 <?php echo $Summary; ?></textarea>
  $Summary = trim( $_POST['ArticleSummary'] );
  echo strlen($Summary);

Answer 1

unicode characters take 2 bytes each and strlen returns the number of bytes in the string, you can transform it to unicode characters and check the length.