hi guys , 
i've faced this example :
<?php
$my_head = str_repeat("°~", 35);
echo $my_head;
?>

so , the length should be 35x2 = 70 !!!
if we echo it :
<?php
$my_head = str_repeat("°~", 35);
echo strlen($my_head); // 105
echo mb_strlen($my_head, 'UTF-8'); // 70
?>

be carefull with characters and try to use mb_* package to make sure everything goes well ...