/**
 * Returns string with newline formatting converted into HTML paragraphs.
 *
 * @author Michael Tomasello <[email protected]>
 * @copyright Copyright (c) 2007, Michael Tomasello
 * @license http://www.opensource.org/licenses/bsd-license.html BSD License
 * 
 * @param string $string String to be formatted.
 * @param boolean $line_breaks When true, single-line line-breaks will be converted to HTML break tags.
 * @param boolean $xml When true, an XML self-closing tag will be applied to break tags (<br />).
 * @return string
 */
function nl2p($string, $line_breaks = true, $xml = true)
{
    // Remove existing HTML formatting to avoid double-wrapping things
    $string = str_replace(array('<p>', '</p>', '<br>', '<br />'), '', $string);
    
    // It is conceivable that people might still want single line-breaks
    // without breaking into a new paragraph.
    if ($line_breaks == true)
        return '<p>'.preg_replace(array("/([\n]{2,})/i", "/([^>])\n([^<])/i"), array("</p>\n<p>", '<br'.($xml == true ? ' /' : '').'>'), trim($string)).'</p>';
    else 
        return '<p>'.preg_replace("/([\n]{1,})/i", "</p>\n<p>", trim($string)).'</p>';
}

http://www.youngcoders.com/share-php-script/26933-nl2p-alternative-nl2br.html

nl2p - alternative to nl2br

PHP