(PHP 4, PHP 5)
session_set_save_handler — Sets user-level session storage functions
session_set_save_handler() sets the user-level session storage functions which are used for storing and retrieving data associated with a session. This is most useful when a storage method other than those supplied by PHP sessions is preferred. i.e. Storing the session data in a local database.
Read function must return string value always to make save handler work as expected. Return empty string if there is no data to read. Return values from other handlers are converted to boolean expression. TRUE for success, FALSE for failure.
Note: The "write" handler is not executed until after the output stream is closed. Thus, output from debugging statements in the "write" handler will never be seen in the browser. If debugging output is necessary, it is suggested that the debug output be written to a file instead.
如果成功则返回 TRUE，失败则返回 FALSE。
Example#1 session_set_save_handler() example
The following example provides file based session storage similar to the PHP sessions default save handler files . This example could easily be extended to cover database storage using your favorite PHP supported database engine.
<?php
function open($save_path, $session_name)
{
global $sess_save_path;
$sess_save_path = $save_path;
return(true);
}
function close()
{
return(true);
}
function read($id)
{
global $sess_save_path;
$sess_file = "$sess_save_path/sess_$id";
return (string) @file_get_contents($sess_file);
}
function write($id, $sess_data)
{
global $sess_save_path;
$sess_file = "$sess_save_path/sess_$id";
if ($fp = @fopen($sess_file, "w")) {
$return = fwrite($fp, $sess_data);
fclose($fp);
return $return;
} else {
return(false);
}
}
function destroy($id)
{
global $sess_save_path;
$sess_file = "$sess_save_path/sess_$id";
return(@unlink($sess_file));
}
function gc($maxlifetime)
{
global $sess_save_path;
foreach (glob("$sess_save_path/sess_*") as $filename) {
if (filemtime($filename) + $maxlifetime < time()) {
@unlink($filename);
}
}
return true;
}
session_set_save_handler("open", "close", "read", "write", "destroy", "gc");
session_start();
// proceed to use sessions normally
?>
As of PHP 5.0.5 the write and close handlers are called after object destruction and therefore cannot use objects or throw exceptions. The object destructors can however use sessions.
It is possible to call session_write_close() from the destructor to solve this chicken and egg problem.
Current working directory is changed with some SAPIs if session is closed in the script termination. It is possible to close the session earlier with session_write_close().