HTTP based uploading using PHP

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PHP

Hi, I want to upload a PDF file to server where a php script is running. I am new to PHP have no idea how to write this script. I cann't use FTP uploading. I have to use HTTP based uploading.
More clarification:
Upload will be done by C++ (I can do that)
Receive will be done in PHP script(Need help here)
Can any one help?

Thanks

UPDATE from OP:

// body contains sent data here
    $body = file_get_contents('php://input');

    //If will execute for install time....
    $StrOneTmp = strstr($body, "HOSTNAME_", FALSE);
    if(FALSE != $StrOneTmp)
    {
        //$StrOneTmp = strstr($body, '_', false);
        $StrOneTmp = strrev($StrOneTmp);
        $StrOneTmp = strstr($StrOneTmp, '_', TRUE);
        $StrOneTmp = strrev($StrOneTmp);
        mkdir($StrOneTmp);
    }

    //This is data
    $StrTmp = strstr($body, "[...]", FALSE);
    if( FALSE != $StrTmp )
    {
        $data = strstr($body, '[', TRUE); //fine

        $HostFolder = $body;
        $HostFolder = strrev($HostFolder);
        $HostFolder = strstr($HostFolder, ']', TRUE);
        $HostFolder = strrev($HostFolder);

        $today = date("dmY-Gis");
        $name = $today . ".log";
        $FilePath = $HostFolder . "\\" . $name;

        $f = fopen($FilePath, "w+");
        if(NULL == $f)
        {
            mkdir($HostFolder);
        }
        $f = fopen($FilePath, "w+");
        fwrite($f, $data);
        fclose($f);
    }
?>