Practice php file Upload, upload pictures cannot open

Practice php File Download, download the picture does not open
$file _name= "Hello.jpg";
if (!file_exists ($file _name))
{
echo "file does not exist";
Return
}
$FP =fopen ($file _name, "R");
Get the download file size
$file _size=filesize ($file _name);
echo $file _size;
The returned file
Header ("Content-type:application/octet-stream");
Returns by byte size
Header ("Accept-ranges:byte");
Return file size
Header ("Accept-length: $file _size");
Here the client's popup dialog box, corresponding to the file name
Header ("Content-disposition:attachment;filename=". $file _name);


$buffer = 1024;
Determine whether the file ends at the end
while (!feof ($FP))
{
echo "1111";
$file _data=fread ($fp, $buffer);
Send some data back to the browser
echo $file _data;
}
Fclose ($FP);
?>


The prompt to open the picture file is: Because this file may be corrupted, or too large

------Solution--------------------
echo $file _size; This sentence is commented out

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