(PHP 4 >= 4.1.0, PHP 5)
hypot — Calculate the length of the hypotenuse of a right-angle triangle
$x
   , float $y
   )
   hypot() returns the length of the hypotenuse of a
   right-angle triangle with sides of length x and
   y, or the distance of the point
   (x, y) from the origin.
   This is equivalent to sqrt(x*x + y*y).
  
xLength of first side
yLength of second side
Calculated length of the hypotenuse