PHP rookie Solver-about file downloads

PHP Beginner Solver--about file download
Hello, everybody. I'm a beginner. Just read the video of the Preach Wisdom Podcast on the file download section, according to the beginning of Han teacher gave the code himself to write again, but why the picture is displayed in the page, rather than from the browser download?

Please, my friends, thank you for your help.



$file _name= "Mao.jpg";
if (!file_exists ($file _name)) {
echo "file does not exist! ";
Return
}
$FP =fopen ($file _name, "R");
$file _size=filesize ($file _name);

Header ("Content-type:application/octet-stream");
Header ("Accept-ranges:bytes");
Header ("Accept-length: $file _size");
Header ("content-disponsition:attachment; Filename= ". $file _name);

$buffer = 1024;
while (!feof ($fp)) {
$file _data=fread ($fp, $buffer);
echo $file _data;
}
Fclose ($FP);
?>

------Solution--------------------
Header ("content-disponsition:attachment; Filename= ". $file _name); There's an n here, so it's invalid.

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