How to set a custom timeout for DNS resolution in cURL in PHP?

To set a custom timeout for DNS resolution in cURL using PHP, you can use the CURLOPT_TIMEOUT and CURLOPT_DNS_CACHE_TIMEOUT options.

Here is an example code snippet:

// Create a new cURL resource
$ch = curl_init();

// Set the URL to fetch
curl_setopt($ch, CURLOPT_URL, "https://example.com");

// Set the DNS resolution timeout in seconds
// This timeout includes the time to resolve the DNS and establish the connection
curl_setopt($ch, CURLOPT_TIMEOUT, 5);

// Set the DNS cache timeout in seconds
// This is the time to keep resolved DNS entries in cache
curl_setopt($ch, CURLOPT_DNS_CACHE_TIMEOUT, 1800);

// Execute the cURL request
$response = curl_exec($ch);

// Check for errors
if ($response === false) {
    echo 'cURL error: ' . curl_error($ch);
}

// Close cURL resource
curl_close($ch);

// Process the response
// ...

In this code snippet, CURLOPT_TIMEOUT is set to 5 seconds, which determines the maximum time to wait for both the DNS resolution and TCP connection establishment. If the timeout is reached during these processes, the cURL request will fail.

CURLOPT_DNS_CACHE_TIMEOUT is set to 1800 seconds (30 minutes), meaning that resolved DNS entries will be kept in cache for that duration, avoiding the need for repeated DNS resolution.