How to switch from curl to multicurl?

Question

PHP

There is too much load on the site, since there are about 20 API requests on the page.
Therefore, I think you need to switch to multithreading. I studied the instructions, but did not understand.
The point is this.
When a response is received from the api, files with cached data are created, from which information is then taken for output.
The query structure is like this.
Code

1)

<?php
$cache_ttl = 21600; // время жизни кэша в секундах
$cache_file_airlines = "tmp/ish.data";
$cache_file_products = "tmp/ish1.data";
$map = function ($array, $from, $to)
{
$result = [];
if (!empty($array) && is_array($array))
{
foreach ($array as $element)
{
$key = $element[$from] ? : null;
$value = $element[$to] ? : null;
if ($key && $value)
{
$result[$key] = $value;
}
}
}
return $result;
};
if (file_exists($cache_file_airlines) && (time() - filemtime($cache_file_airlines)) < $cache_ttl)
{
// берём кэшированные данные
$get_airlines = file_get_contents($cache_file_airlines);
}
else
{
$get_airlines = file_get_contents('https://site.ru/json/airlines.json');
file_put_contents($cache_file_airlines, $get_airlines);
}
$airlines = array_column($dataAER, 'name','iata');

if (file_exists($cache_file_products) && (time() - filemtime($cache_file_products)) < $cache_ttl)
{
// берём кэшированные данные
$response = file_get_contents($cache_file_products);
}
else
{
$ch = curl_init();
curl_setopt(
  $ch,
  CURLOPT_URL,
  "https://site.ru/v3/prices_for_dates?origin=MOW&destination=AER&token=*******&departure_at=" . date('Y-m-d') );
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
"X-Access-Token: **********"
));
$response = curl_exec($ch);
curl_close($ch);

file_put_contents($cache_file_products, $response);
}
$products = json_decode($response, true);
$replace_value = function ($key, $val) use ($airlines)
{
$response = $val;
switch ($key)
{
case 'airline':
$response = $airlines[$val];
break;
}
return $response;
} ?>
<div class="table-responsive" style="overflow-x:hidden;background: var(--responsiv-color)!important; display: flex; flex-direction: column; width: 100%;margin-left: auto; margin-right: auto; list-style-type: none;overflow-y:hidden;">
<?php
if (isset($products['data']) && is_array($products['data']))
{
foreach ($products['data'] as $key => $dataAER)
?>

2)

<?php
$cache_ttl = 21600; // время жизни кэша в секундах
$cache_file_airlines = "tmp/ish2.data";
$cache_file_products = "tmp/ish3.data";
$map = function ($array, $from, $to)
{
$result = [];
if (!empty($array) && is_array($array))
{
foreach ($array as $element)
{
$key = $element[$from] ? : null;
$value = $element[$to] ? : null;
if ($key && $value)
{
$result[$key] = $value;
}
}
}
return $result;
};
if (file_exists($cache_file_airlines) && (time() - filemtime($cache_file_airlines)) < $cache_ttl)
{
// берём кэшированные данные
$get_airlines = file_get_contents($cache_file_airlines);
}
else
{
$get_airlines = file_get_contents('https://site.ru/json/airlines.json');
file_put_contents($cache_file_airlines, $get_airlines);
}
$airlines = array_column($dataSIP, 'name','iata');

if (file_exists($cache_file_products) && (time() - filemtime($cache_file_products)) < $cache_ttl)
{
// берём кэшированные данные
$response = file_get_contents($cache_file_products);
}
else
{
$ch = curl_init();
curl_setopt(
  $ch,
  CURLOPT_URL,
  "https://site.ru/v3/prices_for_dates?origin=MOW&destination=SIP&token=******&departure_at=" . date('Y-m-d') );
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
"X-Access-Token: ******"
));
$response = curl_exec($ch);
curl_close($ch);

file_put_contents($cache_file_products, $response);
}
$products = json_decode($response, true);
$replace_value = function ($key, $val) use ($airlines)
{
$response = $val;
switch ($key)
{
case 'airline':
$response = $airlines[$val];
break;
}
return $response;
} ?>
 <div class="table-responsive" style="overflow-x:hidden;background: var(--responsiv-color)!important; display: flex; flex-direction: column; width: 100%;margin-left: auto; margin-right: auto; list-style-type: none;overflow-y:hidden;">
<?php
if (isset($products['data']) && is_array($products['data']))
{
foreach ($products['data'] as $key => $dataSIP)
?>

The difference is in the names of files with cached data and these variables $dataSIPand $dataAER

Such requests on one page 21

How to combine these requests into one?
Will it reduce the load on the server?
How else can you reduce the load?