error downloading image using php script - php

Question

I wrote this code to download an image from instagram. the image downloaded but it have some errors. that's mean I can download the image but I cant open it
<?php
$linktopage = 'http://instagram.com/p/jTh1cBHG36/';
$sourcecode = file_get_contents( $linktopage );
$sourcecode = substr($sourcecode , strpos($sourcecode, 'og:image') + 19, strlen($sourcecode));
$sourcecode = substr($sourcecode , 0 , strpos($sourcecode, '"'));
$name= substr($sourcecode , strpos($sourcecode, 'com/') + 4, strlen($sourcecode));
$fileToSend = $sourcecode;
header('Content-type: image/jpeg');
header('Content-Disposition: attachment; filename='.$name.'"');
header("Content-Length: ". file_size($fileToSend));
readfile($fileToSend);
?>

Answer 1

Comment the Content-Length line and it will work fine:
//header("Content-Length: ". file_size($fileToSend));
The correct function name is filesize (and I'm not sure if it will work on your URL).
I also see that you are missing a quote after filename=. It should be:
header('Content-Disposition: attachment; filename="'.$name.'"');
So, the working version of your code will be:
$linktopage = 'http://instagram.com/p/jTh1cBHG36/';
$sourcecode = file_get_contents( $linktopage );
$sourcecode = substr($sourcecode , strpos($sourcecode, 'og:image') + 19, strlen($sourcecode));
$sourcecode = substr($sourcecode , 0 , strpos($sourcecode, '"'));
$name= substr($sourcecode , strpos($sourcecode, 'com/') + 4, strlen($sourcecode));
$fileToSend = $sourcecode;
header('Content-type: image/jpeg');
header('Content-Disposition: attachment; filename="'.$name.'"');
//header("Content-Length: ". filesize($fileToSend));
readfile($fileToSend);

Answer 2

The problem is happening because of a typo error.
Typo error was in the following line:
header('Content-Disposition: attachment; filename='.$name.'"');
Due to the wrong name format '_' was getting added to the file extension.
One more addition in the code is for content length which is 2 line only:
$head = array_change_key_case(get_headers($sourcecode, TRUE));
$filesize = $head['content-length'];
Final Working code with typo error fixed:
<?php
$linktopage = 'http://instagram.com/p/jTh1cBHG36/';
$sourcecode = file_get_contents( $linktopage );
$sourcecode = substr($sourcecode , strpos($sourcecode, 'og:image') + 19, strlen($sourcecode));
$sourcecode = substr($sourcecode , 0 , strpos($sourcecode, '"'));
$name= substr($sourcecode , strpos($sourcecode, 'com/') + 4, strlen($sourcecode));
$fileToSend = $sourcecode;
$head = array_change_key_case(get_headers($sourcecode, TRUE));
$filesize = $head['content-length'];
header("Content-type: image/jpeg");
header("Content-Disposition: attachment; filename=".$name);
header("Content-Length: ". $filesize);
readfile($fileToSend);
?>