session.php

<?php
error_reporting(E_ALL);
ini_set('display_errors','On');
class MysqlSessionHandler implements SessionHandlerInterface,SessionIdInterface{
    private PDO $pdo;
    private PDOStatement $readStatement;
    private PDOStatement $writeStatement;
    public function __construct(PDO $pdo){
        $this->pdo = $pdo;  
    }
    private function getNextFreeId(){
        $id = md5(microtime(true));
        $this->readStatement->execute([':sessionId'=>$id]);
        if($this->readStatement->rowCount() > 0){
            $id = $this->getNextFreeId();
        }
        return $id;
    }
    public function create_sid(){
        return $this->getNextFreeId();
    }
    public function close(){

        return true;
    }
    public function open($savePath, $sessionName)
    {
        $sql ="SELECT value FROM sessions WHERE id=:sessionId";
        $this->readStatement = $this->pdo->prepare($sql);
        
        $sql ="INSERT INTO sessions SET value=:value,id=:sessionId ON DUPLICATE KEY UPDATE value=:value";
        $this->writeStatement = $this->pdo->prepare($sql);
      
        return true;
    }
    public function read($id)
    {
       $this->readStatement->execute([':sessionId'=>$id]);
       return (string) $this->readStatement->fetchColumn();
    }
    public function write($id,$data){
        $result = $this->writeStatement->execute([
             ':value'=>$data,
             ':sessionId'=>$id
         ]);
        
         return $result;
     }
     public function destroy($id){
        $deleteSQL = "DELETE FROM sessions WHERE id=:sessionId";
        $statement = $this->pdo->prepare($deleteSQL);
        $result= $statement->execute([':sessionId'=>$id]);
      
       return $result;
    }
    public function gc($maxlifetime){
        $cleanUpSQL ="DELETE FROM sessions WHERE NOW() > DATE_ADD(lastUpdate,INTERVAL ".(int)$maxlifetime." SECOND)";
        return $this->pdo->exec($cleanUpSQL);
    }
}
$pdo = new PDO('mysql:host=localhost;dbname=test;charset=utf8mb4','root','');
$sessionHandler = new MysqlSessionHandler($pdo);
session_set_save_handler($sessionHandler,true);
session_start();

$_SESSION['test'] = 'foo';

$_SESSION['test2'] = [
'test'
];