Not just the @ sign, the whole line is bad programming style.
The more things you embed, the more problems you are going to have when things go wrong.
The line you posted does not check for errors, even though the fopen, and fread could both fail.
If the file you want to read does not exist, you just get no output from this line. You'll spend hours trying to figure out why you get no output.
A much better version is this:
if (!$rFP = fopen($form_data, "rb"))
{
echo 'Could not open file for reading');
}
else
{
if (!$sData = fread($rFP,$form_data_size))
{
echo 'Could not read data');
}
else
{
// Data read ok, process data
$sData = addslashes($sData);
};
};
