Description:
------------
When you hand a variable to the 'to' parameter of the mail() function which has trailing whitespace the PHP variable get altered!

It seems the mail() function is stripping the trailing whitespace by putting a null character at the start of it, but this is somehow getting back into the PHP variable (as if it had been passed by reference?) so the PHP variable contains a null character where the trailing whitespace started before the mail() function was called.

Reproduce code:
---------------
<?php
// to address with trailing space
$to = 'tom@scl.co.uk ';
 
// Output the ASCII code for the last char
// in the $to address string
print("Last char=".ord($to{strlen($to)-1})."\n");
 
// Send a message to the email address in $to
mail($to, "Subject", "Message");

// Output the ASCII code for the last char
// in the $to address string
print("Last char=".ord($to{strlen($to)-1})."\n");
?>

Expected result:
----------------
Last char=32
Last char=32

Actual result:
--------------
Last char=32
Last char=0