Description:
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Documentation for ip2long needs a little more detail.  It says that it returns FALSE if the argument passed is not a valid IP address, and says this returned -1 before version 5.  

It should also mention that if it is passed an empty argument that it will still return -1.

Reproduce code:
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<?php
echo "<br />Result: " . ip2long("10.10.10.10"); // returns long
echo "<br />Result: " . ip2long("not.an.ip.address"); // returns FALSE
echo "<br />Result: " . ip2long(""); // should return FALSE, returns -1
?>

Expected result:
----------------
Result: 168430090
Result:
Result: 

Actual result:
--------------
Result: 168430090
Result:
Result: -1