How to Linkify URLs in a String Using PHP?

Linking URLs in a String Using PHP

When dealing with strings that contain URLs, it is often desirable to turn those URLs into clickable hyperlinks. This can be achieved through PHP's extensive string manipulation capabilities.

Consider the following string:

"Look on http://www.google.com".

The goal is to convert this string into:

"Look on <a href="http://www.google.com">http://www.google.com</a>"

Solution

PHP provides several methods for searching and replacing patterns within strings. To linkify URLs in a string, we can use the following code:

<code class="php">$string = "Look on http://www.google.com";
$string = preg_replace(
    "~[[:alpha:]]+://[^<>[:space:]]+[[:alnum:]/]~",
    "<a href=\"\0\">\0</a>", 
    $string
);</code>

This code utilizes regular expressions to identify valid URLs within the string. The pattern ~[[:alpha:]] ://[^<>[:space:]] [[:alnum:]/]~ searches for strings that start with the "http" protocol, followed by a domain name or IP address, and ending with a slash or other alphanumeric character.

Once a URL is matched, it is replaced with a string that includes an HTML anchor tag () with the URL as the href attribute. The \0 sequence is used as a placeholder for the matched URL.

Compatibility Note

The code provided supports PHP versions 5.3 and above. For versions below 5.3, replace preg_replace with ereg_replace.

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