如何在PHP中打印大字符串

Question

I'm building a web server and i want my php script to transfer large amounts of data. Which method should i use?

I'm talking about over 20 mb sized strings. I tried to echo them but script cannot print more than 5-6 mb after 1-2 minutes. After that I tried to split strings into blocks and print them, still no luck. Compressing didn't work either since the strings are base64 encoded.

As you can see here, i tried to write the data into a file and download it:

$payload = "my large string";
file_put_contents("payload.txt", $payload);
$download_rate = 100;
$file = fopen("payload.txt", "r");
while(!feof($file)) {
    print fread($file, round($download_rate * 1024));
    flush();
    ob_end_clean();
}
fclose($file);

Answer 1

Transferring of data, and printing of data (you mean output in browser?) are two very different things. For transferal you would use the appropriate headers.

What I mean is something like this:

if (ob_get_level()) ob_end_clean(); // switch output buffering off

$path = "payload.txt";

header("Content-Disposition: attachment; filename=\"" . basename($path) . "\"");
header("Content-Type: application/octet-stream");
header("Content-Length: " . filesize($path));

readfile($path);

Nothing complex. Note that the file is downloaded (= transferred) and not rendered in the browser. It's the headers that do the trick and the readfile() of course.

A quote from the readfile() page:

Note:
readfile() will not present any memory issues, even when sending large files, on its own. If you encounter an out of memory error ensure that output buffering is off with ob_get_level().

There's also a slightly more advanced example there, with more headers.