(PHP Extension) HTTP Download in Parallel with Simultaneous Range Requests

Demonstrates how to download a large file with parallel simultaneous requests, where each request downloads a segment (range) of the remote file.

Chilkat PHP Downloads PHP Extension for Windows, Linux, MacOS, Alpine Linux, Solaris

<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

$http = new CkHttp();

// First get the size of the file to be downloaded.
$url = 'https://www.chilkatsoft.com/hamlet.xml';

// resp is a CkHttpResponse
$resp = $http->GetHead($url);
if ($http->get_LastMethodSuccess() == false) {
    print $http->lastErrorText() . "\n";
    exit;
}

$remoteFileSize = $resp->get_ContentLength();

print 'Downloading ' . $remoteFileSize . ' bytes...' . "\n";

// Let's download in 4 chunks.
// (the last chunk will be whatever remains after the 1st 3 equal sized chunks)
$chunkSize = $remoteFileSize / 4;

// The Range header is used to download a range from a resource
// Range: bytes=<range-start>-<range-end>
// or
// Range: bytes=<range-start>-

// We're writing code this way for clarity..
$http1 = new CkHttp();
$http2 = new CkHttp();
$http3 = new CkHttp();
$http4 = new CkHttp();

$sbRange = new CkStringBuilder();
$sbRange->SetString('bytes=<range-start>-<range-end>');
$numReplaced = $sbRange->ReplaceI('<range-start>',0);
$numReplaced = $sbRange->ReplaceI('<range-end>',$chunkSize - 1);
print $sbRange->getAsString() . "\n";
$http1->SetRequestHeader('Range',$sbRange->getAsString());

$sbRange->SetString('bytes=<range-start>-<range-end>');
$numReplaced = $sbRange->ReplaceI('<range-start>',$chunkSize);
$numReplaced = $sbRange->ReplaceI('<range-end>',2 * $chunkSize - 1);
print $sbRange->getAsString() . "\n";
$http2->SetRequestHeader('Range',$sbRange->getAsString());

$sbRange->SetString('bytes=<range-start>-<range-end>');
$numReplaced = $sbRange->ReplaceI('<range-start>',2 * $chunkSize);
$numReplaced = $sbRange->ReplaceI('<range-end>',3 * $chunkSize - 1);
print $sbRange->getAsString() . "\n";
$http3->SetRequestHeader('Range',$sbRange->getAsString());

$sbRange->SetString('bytes=<range-start>-');
$numReplaced = $sbRange->ReplaceI('<range-start>',3 * $chunkSize);
print $sbRange->getAsString() . "\n";
$http4->SetRequestHeader('Range',$sbRange->getAsString());

// Start each range download
// task1 is a CkTask
$task1 = $http1->DownloadAsync($url,'qa_output/chunk1.dat');
$task1->Run();

// task2 is a CkTask
$task2 = $http2->DownloadAsync($url,'qa_output/chunk2.dat');
$task2->Run();

// task3 is a CkTask
$task3 = $http3->DownloadAsync($url,'qa_output/chunk3.dat');
$task3->Run();

// task4 is a CkTask
$task4 = $http4->DownloadAsync($url,'qa_output/chunk4.dat');
$task4->Run();

// Wait for the downloads to complete.
$numLive = 4;
while ($numLive > 0) {
    $numLive = 0;
    if ($task1->get_Live() == true) {
        $numLive = $numLive + 1;
    }

    if ($task2->get_Live() == true) {
        $numLive = $numLive + 1;
    }

    if ($task3->get_Live() == true) {
        $numLive = $numLive + 1;
    }

    if ($task4->get_Live() == true) {
        $numLive = $numLive + 1;
    }

    if ($numLive > 0) {
        // SleepMs is a convenience method to cause the caller to sleep for N millisec.
        // It does not cause the given task to sleep..
        $task1->SleepMs(10);
    }

}

// All should be downloaded now..
// Examine the result of each Download.
$numErrors = 0;
if ($task1->GetResultBool() == false) {
    print $task1->resultErrorText() . "\n";
    $numErrors = $numErrors + 1;
}

if ($task2->GetResultBool() == false) {
    print $task2->resultErrorText() . "\n";
    $numErrors = $numErrors + 1;
}

if ($task3->GetResultBool() == false) {
    print $task3->resultErrorText() . "\n";
    $numErrors = $numErrors + 1;
}

if ($task4->GetResultBool() == false) {
    print $task4->resultErrorText() . "\n";
    $numErrors = $numErrors + 1;
}

if ($numErrors > 0) {

    exit;
}

// All downloads were successful.
// Compose the file from the parts.
$fac = new CkFileAccess();
$success = $fac->ReassembleFile('qa_output','chunk','dat','qa_output/hamlet.xml');
if ($success == false) {
    print $fac->lastErrorText() . "\n";
}
else {
    print 'Success.' . "\n";
}

// Let's download in the regular way, and then compare files..
$success = $http->Download($url,'qa_output/hamletRegular.xml');

// Compare files.
$bSame = $fac->FileContentsEqual('qa_output/hamlet.xml','qa_output/hamletRegular.xml');
print 'bSame = ' . $bSame . "\n";

?>