find the biggest difference between numbers

i have 7 numbers in random from -100 to 100, from those seven numbers i need to find the biggest diference between each them

example:

-50 , 60 , -4 , 80 , 25, -34, 15 

the output will be 130 -50 and 80 is the biggest diference

but i need in php

i have tried echo max(rand(-100, 100));

but it is not the output im looking for

this i tried too:

$myarray = array(
  'this' => 2, 
  'that' => 14, 
  'them' => -5, 
  'other' => 200, 
  'nothing' => 42, 
  'somethingelse' => 1, 
  'you' => 10, 
  'me' => 30);

foreach ($myarray as $key => $value) {
  if (!isset ($min) || $value < $min) { $min = $value; }
  if (!isset ($max) || $value > $max) { $max = $value; }
}

$diff = $max - $min;
echo $diff;

any suggestion?