Programming PHP

php.ini file) and the name of the variable containing the PHP session ID (which
defaults to PHPSESSID and can be changed in the php.ini file by setting session.name).
Our open handler simply connects to the database and sets the global variable $table
to the name of the database table that holds the session information:
function open ($save_path,$session_name) {
global $table;
mysql_connect('localhost');
mysql_select_db($save_path);
$table = $session_name;
return true;
}
Once a session has been opened, the read and write handlers are called as necessary
to get the current state information and to store that state in a persistent manner.
The read handler is given the session ID, and the write handler is called with the session’s
ID and the data for the session. Our database read and write handlers query
and update the database table:
function read($session_id) {
global $table;
$result = mysql_query("SELECT value FROM $table
WHERE session_id='$session_id'");
if($result && mysql_num_rows($result)) {
return mysql_result($result,0);
} else {
error_log("read: ".mysql_error( )."\n",3,"/tmp/errors.log");
return "";
}
}
function write($session_id, $data) {
global $table;
$data = addslashes($data);
mysql_query("REPLACE INTO $table (session_id,value)
VALUES('$session_id','$data')")
or error_log("write: ".mysql_error( )."\n",3,"/tmp/errors.log");
return true;
}
Complementing the open handler is the close handler, which is called after each
page’s script is done executing. It performs any cleanup necessary when closing a
session (usually very minimal). Our database close handler simply closes the database
connection:
function close() {
mysql_close();
return true;
}
186 | Chapter 7: Web Techniques
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