C Function to check occurrence of a character in a particular string

/*
 * Returns index of the first occurrence of the character
 * else returns -1 if the character is not present
 */


int checkChar(char *string, char ch)
{
        int index;

         if(string == NULL)
                    return -1;
         for (index = 0 ; index < strlen(string); index++)
         {
                if(string[index] == ch)
                       break;
           }
           if(index == strlen(string)
                      return -1;
          return index;
}