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21 years ago
I spent a while trying to use SOCK_RAW to send ICMP request packets so i could ping. This however lead me to need the internet checksum written as a php function, which was a little hard because of the way PHP handles variable types. Anyway, to save others the effort heres what i came up with, this returns Checksum for $data

<?PHP
// Computes Internet Checksum for $data
// will return a 16-bit internet checksum for $data
function inetChecksum($data)
{
    // 32-bit accumilator, 16 bits at a time, adds odd bit on at end
    for($i=0;$i<strlen($data);$i += 2)
    {
        if($data[$i+1]) $bits = unpack('n*',$data[$i].$data[$i+1]);
        else $bits = unpack('C*',$data[$i]);
        $sum += $bits[1];
    }
    
    // Fold 32-bit sum to 16 bits 
    while ($sum>>16) $sum = ($sum & 0xffff) + ($sum >> 16);
    $checksum = pack('n1',~$sum);
    return $checksum;
}
?>

And with this i was able to construct a correct PING Request.
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