If you want to convert an integer into an English word string, eg. 29 -> twenty-nine, then here's a function to do it.
Note on use of fmod()
  I used the floating point fmod() in preference to the % operator, because % converts the operands to int, corrupting values outside of the range [-2147483648, 2147483647]
I haven't bothered with "billion" because the word means 10e9 or 10e12 depending who you ask.
The function returns '#' if the argument does not represent a whole number.
<?php
$nwords = array( "zero", "one", "two", "three", "four", "five", "six", "seven",
                   "eight", "nine", "ten", "eleven", "twelve", "thirteen",
                   "fourteen", "fifteen", "sixteen", "seventeen", "eighteen",
                   "nineteen", "twenty", 30 => "thirty", 40 => "forty",
                   50 => "fifty", 60 => "sixty", 70 => "seventy", 80 => "eighty",
                   90 => "ninety" );
function int_to_words($x) {
   global $nwords;
   if(!is_numeric($x))
      $w = '#';
   else if(fmod($x, 1) != 0)
      $w = '#';
   else {
      if($x < 0) {
         $w = 'minus ';
         $x = -$x;
      } else
         $w = '';
      if($x < 21)   $w .= $nwords[$x];
      else if($x < 100) {   $w .= $nwords[10 * floor($x/10)];
         $r = fmod($x, 10);
         if($r > 0)
            $w .= '-'. $nwords[$r];
      } else if($x < 1000) {   $w .= $nwords[floor($x/100)] .' hundred';
         $r = fmod($x, 100);
         if($r > 0)
            $w .= ' and '. int_to_words($r);
      } else if($x < 1000000) {   $w .= int_to_words(floor($x/1000)) .' thousand';
         $r = fmod($x, 1000);
         if($r > 0) {
            $w .= ' ';
            if($r < 100)
               $w .= 'and ';
            $w .= int_to_words($r);
         }
      } else {    $w .= int_to_words(floor($x/1000000)) .' million';
         $r = fmod($x, 1000000);
         if($r > 0) {
            $w .= ' ';
            if($r < 100)
               $word .= 'and ';
            $w .= int_to_words($r);
         }
      }
   }
   return $w;
}
?>
Usage:
<?php
echo 'There are currently '. int_to_words($count) . ' members logged on.';
?>