encryption problems

Hi, I use the php3 release on an Apache server. I tried to create an authentification script. I used the C function "crypt" but when I crypted my password to compare one I have into my database, the crypted string was always different. I crypted many time my string: everytime the result was different. Then I decided to use the PHP function "encrypt" but the server returned the following message: "Fatal error: Call to unsupported or undefined function encrypt() in /directory/script.php3 on line 3". The function is called as follows: $Query="UPDATE table SET field1 = '" . encrypt($data,2,$key) . "' WHERE field2='$value';"; (the famous line 3) What sould be the problem? Thanks, Olivier LALOUX