function activateImages($string)
{
    $pattern = "@http[s]?\://[a-zA-Z0-9\-\.\_\/]+\.(jpg|gif|png|jpeg)@i";
    $replacement = '<a href="\0"><img class="resized-image" src="\0" border="0" alt="Bild"/></a>';
    return preg_replace($pattern,$replacement,$string);

}

function activateURLs($string)
{
    $pattern = '@(?<!src=")(?<!href=")http[s]?\://[\/\w\.\_\-]+\.[a-z0-9A-Z\.]{2,5}@i';
    $replacement = '<a href="\0">\0</a>';
    return preg_replace($pattern,$replacement,$string);
}