Convert URLs To Links Without RegEx - PHP

convert_urls.php

<?php
/**
 * Convert URLs To Links Without RegEx
 * 
 * @author  David Miles
 * @link    https://gist.github.com/amereservant
 * 
 * After trying several RegEx patterns to try and match URLs and all of them failing to
 * accurately match them, I decided to take a simplier approach.  Since URLs are continuous
 * strings and begin with a given string (http in this case), All I had to do was use simple
 * string functions to identify the beginning and end of each URL, then replace them accordingly.
 * 
 * It may be possible to simplify these and I will update this GIST if anyone offers such a revision,
 * but my hope is it helps those who have been frustrated with regex patterns not working and this
 * works great for them.
 */
/**
 * Get URLs From String
 *
 * This function takes the given string and searches for the beginning of a URL ('http'),
 * starting at the $start position in that string.  If it finds a match, then it will
 * try to determine the end of the URL as such:
 *  1) A blank space proceeding the URL.  If one is found, it will filter for a newline
 *     character since one might appear after it and correct the string accordingly.
 *  2) The end of the given string.  If the url extends to the end of the string, 
 *     this will be used to determine the end.
 *
 * This function should only be called in a loop by the parse_links function.
 *
 * @param   string  $content    The string to search for urls in
 * @param   integer $start      An offset to determine where to begin searching for the
 *                              url in the string.
 * @return  array|bool          An array with the URL and end position
 */
function _getURLs($content, $start)
{
    // Look for the beginning of an URL
    if( ($begin = strpos($content, 'http', $start)) !== FALSE )
    {
        // Look for a space following the URL
        $end = strpos($content, ' ', $begin);

        // If a space was found ...
        if( $end != 0 )
        {
            $string = substr($content, $begin, ($end - $begin));
            // Filter for newline characters
            $maybe_nl = explode("\n", $string);

            if( count($maybe_nl) > 1 )
            {
                // The URL *should* be the first parameter and trimmed for use
                $string = $maybe_nl[0];
                // Reduce the end position value for all additional characters that
                // may proceed the newline character
                for($i=1;$i < count($maybe_nl);$i++)
                    $end = $end - strlen($maybe_nl[$i]);
            }
            return array($string, $end);
        } else {
            return array(substr($content, $begin, (strlen($content)-$begin)), strlen($content));
        }

    }
    // No (more) URLs in the string, return false
    return false;
}

/**
 * Parse Links
 *
 * Takes the given string and locates the urls in the string, then replaces them with
 * proper HTML tags to make them hyperlinks.
 *
 * @param   string  $content    The content to convert urls into hyperlinks in
 * @return  string              The input string with urls converted into hyperlinks
 */
function parse_links($content)
{
    $urls = array(); // Store found URLs here so they can be replaced
    $start = 0;

    // Loop over the string and find all urls
    while( (($url = _getURLs($content, $start)) !== FALSE) && ($start < strlen($content)) )
    {
        $urls[] = $url[0];
        $start   = $url[1];
    }
    // Replace all found URLs with HTML tags
    foreach($urls as $url)
        $content = str_replace($url, sprintf('<a href="%s" target="_blank">%1$s</a>', $url), $content);

    return $content;
}