fopen
$fp = fopen("download.php","rb");	while(!feof($fp)){		echo "fopen: ".fgets($fp);	}	fclose($fp);说明:
对于fgets($handle,$length);
fgets是读取一行,返回$length-1长度的数据。
fgetc($handle)是读一个字节。
file
$lines = file("download.php");	foreach($lines as $line){		echo "file: ".$line;	}file_get_contents
$content = file_get_contents("download.php");echo "get_contents: ".$content;readfile 据说readfile是不占php线程本身内存的。
echo "readfile: ";	readfile("download.php");	flush();