(PHP 4 >= 4.0.2, PHP 5)
strncasecmp — Binary safe case-insensitive string comparison of the first n characters
$str1
   , string $str2
   , int $len
   )This function is similar to strcasecmp(), with the difference that you can specify the (upper limit of the) number of characters from each string to be used in the comparison.
str1
     The first string.
str2
     The second string.
len
     The length of strings to be used in the comparison.
   Returns < 0 if str1 is less than
   str2; > 0 if str1 is
   greater than str2, and 0 if they are equal.