How to Mimic Stack Overflow\'s Auto-Link Behavior in PHP?

Mimicking Stack Overflow's Auto-Link Behavior in PHP

Many Stack Overflow users have expressed their admiration for the automatic linking functionality of the platform. This article explores how to replicate such behavior in PHP, enabling you to transform URLs into visually appealing links within your own text.

The Auto-Link Regex

The following PHP function utilizes a regular expression pattern from Daring Fireball to identify URLs in text:

<code class="php">function auto_link_text($text)
{
   $pattern  = '(?i)\b((?:[a-z][\w-]+:(?:/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:\'"",<>?«»“”‘’]))';
...
}</code>

Formatting the Links

Once a URL is identified, the function parses it to extract the host and path. This information is then used to create the link text, which is displayed to the user:

<code class="php">...
$text       = parse_url($url, PHP_URL_HOST) . parse_url($url, PHP_URL_PATH);
$text       = preg_replace("/^www./", "", $text);
$last       = -(strlen(strrchr($text, "/"))) + 1;
...</code>

Usage Example

To use the function, simply pass your text to it as an argument:

<code class="php">$text = "...";
$linked_text = auto_link_text($text);</code>

Output

The function will return the input text with URLs converted into HTML links:

Input: This is my text. Check This out http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior

Output: This is my text. Check This out <a href="http://www.stackoverflow.com/questions/1925455/how-to-mimic-stackoverflow-auto-link-behavior">stackoverflow.com/questions/1925455/...</a>

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