Finding a regular expression solution

Find a regular expression
Find a regular expression substitution
Baidu
Baidu as a label outside the string

------Solution--------------------

PHP Code

$s = ' Baid,baidu,baidu,google,baidu  Baidu  sdfsdf www.baidu.com '; Echo preg_replace ("/(?
  
   \\1 ", $s);
------Solution--------------------
$search  = Array ("/(. *)" ([^\.] Baidu[^\.]) (.*)/", "/(.*)([^\.] Baid[^\.]) (.*)/", "/(.*)([^\.] Google[^\.]) (.*)/");
$replace = "\$1$";
$str = ' Baidu baid  12312 Google ';
$res = Preg_replace ($search, $replace, $STR);
Exit ($res);

------Solution--------------------
It seems that PHP has a reverse pre-check, so that, very simple can be solved ...:D
Float away ...
