Description:
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Using copy() or stream_copy_to_stream() fails on Windows with files over 4GB, even if the underlying volume (NTFS) supports it and Windows + PHP are 64 bit.

Test script:
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<?php
	//Both files must be on an NTFS volume. You may use the same volume.
	$src='C:/temp/4G.src.bin';
	$dst='C:/temp/4G.dst.bin';
	define('SIZE_4G',0x100000000);

	@unlink($src);
	//Create file and append random content at the 4GB boundary
	exec('fsutil file createnew ' . escapeshellarg($src) . ' ' . (SIZE_4G-0x100));
	$fp=fopen($src,'ab');
	fwrite($fp,random_bytes(0x200));
	fclose($fp);
	copy($src,$dst);
	if(filesize($src)!==filesize($dst)){die('Files have different sizes!');}
	$f1=fopen($src,'rb') or die('src open failed');
	$f2=fopen($dst,'rb') or die('dst open failed');
	//Seek to 4 GB boundary, as this is the location where the problem occurs
	fseek($f1,SIZE_4G-0x100,SEEK_SET);
	fseek($f2,SIZE_4G-0x100,SEEK_SET);
	echo (fread($f1,0x200)===fread($f2,0x200)?'Identical':'Copy failed');
	fclose($f1);
	fclose($f2);


Expected result:
----------------
The functions should copy files and streams as-is and the script should print "Identical"

Actual result:
--------------
Script prints "Copy failed"

Only the first 4 GB of the source file are copied.
This is actually done repeatedly until the destination is as large as the source. So if the file is 13 GB, the destination will contain the first 4 GB of the source 3 times, followed by the first GB again.

using "fwrite($b,fread($a,$buffer))" to manually copy files works.