PHP curl_multiexec apache限制?

我有这个PHP代码:

test2.php

ini_set('max_execution_time', '900');
ini_set('memory_limit', '2048M');
$start = microtime(true);

$mh = curl_multi_init();
$handles = array();

// create several requests
for ($i = 0; $i < 50; $i++) {
    $ch = curl_init();

    $rand = rand(5,25); // just making up data to pass to script
    curl_setopt($ch, CURLOPT_URL, "http://example.com/test-3.php?time=$rand");
    curl_setopt($ch, CURLOPT_HEADER, 0);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_TIMEOUT, 30);

    curl_multi_add_handle($mh, $ch);
    $handles[] = $ch;
}

// execute requests and poll periodically until all have completed
$isRunning = null;
do {
    curl_multi_exec($mh, $isRunning);
} while ($isRunning > 0);

// fetch output of each request
$outputs = array();
for ($i = 0; $i < count($handles); $i++) {
    $outputs[$i] = trim(curl_multi_getcontent($handles[$i]));
    curl_multi_remove_handle($mh, $handles[$i]);
}

curl_multi_close($mh);

print_r('<pre>');
print_r($outputs);
print_r('</pre>');

printf("Elapsed time: %.2f seconds\n", microtime(true) - $start);

test3.php

 sleep(5);
 echo time();

每次我访问test-2.php时,通过URL(apache)最多只能接收10个输出

Array
(
    [0] => 1599904635
    [1] => 1599904635
    [2] => 1599904635
    [3] => 1599904635
    [4] => 1599904635
    [5] => 1599904635
    [6] => 1599904635
    [7] => 1599904635
    [8] => 1599904635
    [9] => 1599904635
    [10] => 
    [11] => 
    [12] => 
    [13] => 
    [14] => 
    [15] => 
    [16] => 
    [17] => 
    [18] => 
    [19] => 
    [20] => 
    [21] => 
    [22] => 
    [23] => 
    [24] => 
    [25] => 
    [26] => 
    [27] => 
    [28] => 
    [29] => 
    [30] => 
    [31] => 
    [32] => 
    [33] => 
    [34] => 
    [35] => 
    [36] => 
    [37] => 
    [38] => 
    [39] => 
    [40] => 
    [41] => 
    [42] => 
    [43] => 
    [44] => 
    [45] => 
    [46] => 
    [47] => 
    [48] => 
    [49] => 
)

Elapsed time: 5.02 seconds 

但如果我运行test4.php中的代码

exec('php /test-2.php',$output);
print_r($output);

正在显示所有50。。。但每次我尝试通过URL运行时,最多只能运行10。。。有什么办法可以提高限额吗?