Why doesn't exec output anything, although there is output through the command line?

Question

PHP

<?php

$returnStrings = [];
$returnCode = 0;
$e = exec('cd /tmp && curl --connect-timeout 10 --max-time 10 --raw --fail --remote-name http://site.ru/123.png', $returnStrings, $returnCode);

var_dump($e);
var_dump($returnStrings);
var_dump($returnCode);

Why are both $e and $returnStrings empty? Although the same command typed in the shell (putty), i.e.:

cd /tmp && curl --connect-timeout 10 --max-time 10 --raw --fail --remote-name http://site.ru/123.png

displays everything as it should: both the progress of curl and its error message (HTTP 503) with code 22.
PS Only $returnCode is not empty (== 22 in my example).
PPS I suspect that the point is that there is more than one command (but it's not clear how this interferes with php), but then how can curl specify the root folder to save the file?

Answer 1

how then curl'u specify the root folder to save the file?

You cddon't need it here at all.

$ curl --help | grep -i "\-o,"
 -o, --output <file> Write to file instead of stdout
 -O, --remote-name   Write output to a file named as the remote file

Answer 2

Do you read manuals?
php.net/manual/en/function.exec.php
;)