Remplacer les occurences d'une variable

function clickable_link($text)
{
# this functions deserves credit to the fine folks at phpbb.com

$text = preg_replace('#(script|about|applet|activex|chrome):#is', "\\1:", $text);

// pad it with a space so we can match things at the start of the 1st line.
$ret = ' ' . $text;

// matches an "xxxx://yyyy" URL at the start of a line, or after a space.
// xxxx can only be alpha characters.
// yyyy is anything up to the first space, newline, comma, double quote or <
$ret = preg_replace("#(^|[\n ])([\w]+?://[\w\#$%&~/.\-;:=,?@\[\]+]*)#is", "\\1<a href=\"\\2\" target=\"_blank\">\\2</a>", $ret);

// matches a "www|ftp.xxxx.yyyy/zzzz" kinda lazy URL thing
// Must contain at least 2 dots. xxxx contains either alphanum, or "-"
// zzzz is optional.. will contain everything up to the first space, newline,
// comma, double quote or <.
$ret = preg_replace("#(^|[\n ])((www|ftp)\.[\w\#$%&~/.\-;:=,?@\[\]+]*)#is", "\\1<a href=\"http://\\2\" target=\"_blank\">\\2</a>", $ret);

// matches an email@domain type address at the start of a line, or after a space.
// Note: Only the followed chars are valid; alphanums, "-", "_" and or ".".
$ret = preg_replace("#(^|[\n ])([a-z0-9&\-_.]+?)@([\w\-]+\.([\w\-\.]+\.)*[\w]+)#i", "\\1<a href=\"mailto:\\2@\\3\">\\2@\\3</a>", $ret);

// Remove our padding..
$ret = substr($ret, 1);
return $ret;
}