session_reset()

(PHP 5 >= 5.6.0, PHP 7)

用原始值重新初始化会话数组

说明

session_reset(void): bool

session_reset()使用存储在会话存储中的原始值重新初始化会话。该函数需要一个活动会话，并丢弃$_SESSION中的更改。

返回值

成功时返回TRUE，或者在失败时返回FALSE。

更新日志

参见

• $_SESSION
• Thesession.auto_startconfiguration directive
• session_start()启动新会话或者重用现有会话
• session_abort()中断会话阵列更改并完成会话
• session_commit()session_write_close 的别名

First of all you should execute this code :
<?php
  session_start();
  $_SESSION["A"] = "Some Value";
?>
then you should execute this one : 
<?php
  start_session();
  $_SESSION["A"] = "Some New Value"; // set new value
  session_reset(); // old session value restored
  echo $_SESSION["A"];
  //Output: Some Value
?>
That is because session_reset() is rolling back changes to the last saved session data, which is their values right after the session_start().

first create a session variable
<?php
  session_start();
  $_SESSION["A"] = "Some Value";
  echo $_SESSION["A"];
  //Output: Some Value
  //if you need to rollback the session values after seting new value to session variables use session_reset()
  $_SESSION["A"] = "Some New Value"; // set new value
  
  session_reset(); // old session value restored
  echo $_SESSION["A"];
  //Output: Some Value
?>