title: PHP's Infinit value in Bitwise Operations returns strange values
body: <p>Today I just made an interesting discovery while testing what happens calculating bitwisely in php like <code>INF ^ 0</code> (<code>^</code> => Bitwise Operator for Exclusive OR (XOR)) what gave me <code>int(-9223372036854775808)</code> => greatest possible negative value in a 64-Bit system. </p>
  
  <p>But then I was asking myself: "Why is the result going negative in XOR when the "positive infinit" means <code>9223372036854775807</code> (63 Bits on <code>1</code> with a leading <code>0</code>) and 0 (64 Bits on <code>0</code> => <code>0 xor 0 = 0</code>) What is PHP's infinit value though and what is the calculation behind it? And why do I get a (correct?) negative value when I use "negative infinit"(A leading <code>1</code> against a leading <code>0</code> on 0 => <code>1 xor 0 = 1</code>?". </p>
  
  <p>Another interesting point is that this just happens on PHP Version 5.5.9-1, and not e.g. on 5.3.x. and 5.6.x (where i've tested it)! Maybe someone has an idea what happens there? Tested it on three versions but just mine (5.5.9-1) gives those results:</p>
  
  <p><a href="https://i.stack.imgur.com/nyDGO.png" rel="noreferrer"><img src="https://i.stack.imgur.com/nyDGO.png" alt="Bitwise operations"></a></p>
  
  <p>Just to let you guys know, it's just an abstract playaround i've done for fun but I find it's interesting. Maybe someone can help here or explain me a wrong thought I have? Just tell me if someone needs more informations about anything!</p>
  
  <p>EDIT: Accordingly to jbafford it would be great to get a complete answere, so i'll just quote him: <code>why does 5.5 and 5.6 result in PHP_INT_MIN, and everything else return 0?</code></p>