CRC32 From C++/C# to PHP
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I'm not good at algorithms like CRC32, MD5 etc. so I'm even having difficulty asking the question :)

Basically there is a C# application that uses

    [DllImport("Crc32.dll")]
    private static extern UInt32 CRC32Calc(UInt32 crc32, byte[] buffer, uint length);


and further down in the code uses it in a method `Generate` like this

    UInt32 crc = CRC32Calc(crcSeed, rawData, (uint)rawData.Length);

while using a certain `crcSeed` value.

My job is to rework the entire `Generate` method into a PHP function while preserving the correct CRC calculation.

I think that the PHP's 

    int crc32 ( string $str )

function will not work because I can't set the crcSeed. So my question is:

how can I make the exact crc32 calculation in PHP without resorting to outside dll's etc. so I can use the code an a Linux machine.