如何在 PHP 中從不同格式的 URL 中提取基本網域？

How to Extract the Primary Domain Name from a Variety of URL Formats in PHP

Introduction:

When working with URLs, it is often necessary to extract the primary domain name, excluding any subdomains. This can be a challenging task due to the wide range of URL formats that exist.

Solution:

Fortunately, there is a relatively straightforward solution using a combination of PHP functions. By utilizing parse_url and some string manipulation techniques, we can effectively extract the primary domain name from any URL format.

Step 1: Parse the URL

Using parse_url, we can extract the host part of the URL, which includes both the primary domain and any subdomains.

<code class="php">$info = parse_url($url);
$host = $info['host'];</code>

Step 2: Separate the Host Name and TLD

We then split the host string into an array based on periods using the explode function. The second to last string in the array represents the hostname, while the last string represents the top-level domain (TLD).

<code class="php">$host_names = explode(".", $host);
$bottom_host_name = $host_names[count($host_names)-2] . "." . $host_names[count($host_names)-1];</code>

Step 3: Combine the Hostname and TLD

By concatenating the hostname and TLD strings, we obtain the primary domain name.

<code class="php">echo $bottom_host_name;</code>

Explanation:

• parse_url effectively extracts the host portion of the URL, including subdomains.
• explode breaks the host into an array based on periods, allowing isolation of hostname and TLD.
• count determines the number of elements in the array to identify the second-to-last string (hostname) and last string (TLD).
• Concatenation combines the hostname and TLD into the primary domain name.

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