The Cyrillic Character Problem in PHP

The strlen function, like many other PHP string functions, does not work correctly with Cyrillic characters - it counts each Cyrillic letter twice:

php<?php
  echo strlen('абвгд'); // will output 10, not 5
?>

Therefore, for strings that contain or potentially may contain problematic characters, use the mb_strlen function - it will work correctly:

php<?php
  echo mb_strlen('абвгд'); // will output 5
?>