<?php
$header = <<< LOB
Reply-To: __Reply-To
Bounces_to: __Bounce
Message-ID: <__Chr(__Rand(97,122))__Chr(__Rand(98,122)).__X-Mailer@__From_dn>
X-BFI: __Chr(__Rand(97,122))__Chr(__Rand(98,122))
From: __To
LOB;
 
//echo  preg_replace('/__Chr\(__Rand\((\d+),(\d+)\)\)/', eval(chr(rand($1))), $header);
 
function charCallback($matches){
$charOne = (int)$matches[1];
$charTwo = (int)$matches[2];
return chr(rand($charOne,$charTwo));
}
 
echo  preg_replace_callback('/__Chr\(__Rand\((\d+),(\d+)\)\)/', 'charCallback', $header);
 
 
//echo chr(rand(97,122));
 

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