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Extracting domain names from URLs is a common requirement in web development. PHP offers many functions for string manipulation, and the stristr function can be used to extract and work with domain names in URLs. In this article, we will explore how to use stristr to achieve this goal.
stristr is a PHP string function used to find the first occurrence of a substring and return all content from that point to the end of the string. Unlike strpos, stristr is case-insensitive, which is particularly convenient when working with domain names, as they are generally not case-sensitive.
<span><span><span class="hljs-title function_ invoke__">stristr</span></span><span>(</span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$haystack</span></span><span>, </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$needle</span></span><span>, </span><span><span class="hljs-keyword">bool</span></span><span> </span><span><span class="hljs-variable">$before_needle</span></span><span> = </span><span><span class="hljs-literal">false</span></span><span>): </span><span><span class="hljs-keyword">string</span></span>|</span><span><span class="hljs-literal">false</span></span><span>
</span></span>$haystack: The target string, usually the URL from which we want to extract information.
$needle: The substring to search for. Here we use "://", which helps determine the starting position of the domain name.
$before_needle: Optional. If set to true, it returns the content before the match; if false (default), it returns the matched part and everything after it.
Next, let's demonstrate extracting a domain name from a URL using stristr. Suppose we have the following URL:
<span><span><span class="hljs-variable">$url</span></span><span> = </span><span><span class="hljs-string">"https://www.example.com/path/to/page?query=123"</span></span><span>;
</span></span>We want to extract the domain part, which is www.example.com.
<span><span><span class="hljs-meta"><?php</span></span><span>
</span><span><span class="hljs-variable">$url</span></span><span> = </span><span><span class="hljs-string">"https://www.example.com/path/to/page?query=123"</span></span><span>;
</span></span>
<p></span>// Use stristr to find the part after '://'<br>
<br>
$domain_part = stristr($url, '://');</p>
<p>// If found, remove '://' and the path<br>
<br>
if ($domain_part !== </span>false) {<br>
// Remove '://' and take the substring before the first '/'<br>
<br>
$domain = substr($domain_part, 3, strpos($domain_part, '/') - 3);<br>
echo "Domain is: " . </span>$domain;<br>
} else {<br>
echo "Invalid URL format";<br>
}<br>
?><br>
</span>stristr($url, '://'): First, we use stristr to find '://', which marks the start of the domain in the URL. stristr returns the portion after '://', or false if not found.
substr($domain_part, 3, strpos($domain_part, '/') - 3): After locating '://', we use substr and strpos to extract the domain. substr starts from the third character after '://' up to the first '/' in the URL.
echo "Domain is: " . $domain;: Finally, we output the extracted domain name.
URL Format: We assume the input URL is valid and properly formatted. If the URL lacks '://', stristr will not work correctly. It is recommended to validate the URL or include error handling logic.
Subdomain Considerations: If the URL contains a subdomain, such as blog.example.com, the code will still correctly extract the full domain, including the subdomain.
Different Protocols: If the URL uses different protocols (e.g., http, https, ftp), stristr still works because it is case-insensitive.
Using the stristr function to extract domain names from URLs is a simple and efficient method. By combining stristr with substr, we can easily locate and extract the domain portion. This approach is particularly useful when dealing with URLs that include paths and query parameters while ensuring case-insensitive handling.
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