<?php
    $data = explode(" ","[9/23/11 11:09:53:632 CEST] 0000005b FormLoginExte 3 Form based login: userid/password present in the form. User is: user1");
    
    //data now contains all the info that you need
    var_dump($data);
    ?>

array(17) {
  [0]=>
  string(8) "[9/23/11"
  [1]=>
  string(12) "11:09:53:632"
  [2]=>
  string(5) "CEST]"
  [3]=>
  string(8) "0000005b"
  [4]=>
  string(13) "FormLoginExte"
  [5]=>
  string(1) "3"
  [6]=>
  string(4) "Form"
  [7]=>
  string(5) "based"
  [8]=>
  string(6) "login:"
  [9]=>
  string(15) "userid/password"
  [10]=>
  string(7) "present"
  [11]=>
  string(2) "in"
  [12]=>
  string(3) "the"
  [13]=>
  string(5) "form."
  [14]=>
  string(4) "User"
  [15]=>
  string(3) "is:"
  [16]=>
  string(5) "user1"
}