j'ai un probleme dans mon model.php

slt tt le monde,
j'ai fini les tutos développer un site de A a Z,
mais j'ai un problème lors je poste un nouveau article, dans l'accueil normalement je récupère le dernier en premier l'ordre par la date
mais cela comment faire dans cet formation développer un site de A a Z?
aider moi svp une semain de vérification sans resultat.

voici mon fichier model.php

<?php
class Model{

    static $connections = array();
    public $conf = 'default';
    public $table = false;
    public $db;
    public $primaryKey = 'id';
    public $id;
    public $errors = array();
    public $form;
    public function __construct(){
        //j'initialise quelque variable
        if($this->table=== false){
            $this->table = strtolower(get_class($this)).'s';
        }

        // Jme connect a la base
        $conf = Conf::$databases$this->conf];
        if(isset(Model::$connections$this->conf])){
            $this->db = Model::$connections$this->conf];
            return true;
        }
        try{
        $pdo = new PDO(
        'mysql:host='.$conf'host'].';dbname='.$conf'database'].';',
        $conf'login'],
        $conf'password'],
        array(PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8')
        );

        $pdo->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_WARNING);

        Model::$connections$this->conf] = $pdo;
        $this->db = $pdo;
    }catch(PDOException $e){
            if(Conf::$debug >= 1){
                die($e->getMessage());
            }else{
                die('Impossible de se connecter à la base de donnée');
            }
        }

    }

    public function find($req = array()){
        $sql = 'SELECT ';

        if(isset($req'fields'])){
            if(is_array($req'fields'])){
                $sql .= implode(', ',$req'fields']);
            }else{
                $sql .= $req'fields'];
            }
        }else{

            $sql.='*';

        }

        $sql .= ' FROM '.$this->table.' as '.get_class($this).' ';

        //contruction de la condition
        if(isset($req'conditions'])){
            $sql .= 'WHERE ';
            if(!is_array($req'conditions'])){
                $sql .= $req'conditions'];
            }else{
                $cond = array();
                foreach($req'conditions'] as $k=>$v){
                        if(!is_numeric($v)){
                            $v = '"'.mysql_escape_string($v).'"';
                        }
                        $cond] = "$k=$v";
                }
                $sql .= implode(' AND ',$cond); 

            }

        }

        if(isset($req'limit'])){
            $sql .= 'LIMIT '.$req'limit'];

        }

        $pre = $this->db->prepare($sql);
        $pre->execute();
        return $pre->fetchAll(PDO::FETCH_OBJ);
    }

    public function findFirst($req){
        return current($this->find($req));
    }

    public function findCount($conditions){
        $res = $this->findFirst(array(
            'fields' => 'COUNT('.$this->primaryKey.') as count',
            'conditions' => $conditions
            ));

        return $res->count;

    }

    public function delete($id){
        $sql = "DELETE FROM {$this->table} WHERE {$this->primaryKey} = $id";
        $this->db->query($sql);
    }

    public function save($data){
        $key = $this->primaryKey;
        $fields = array();
        $d = array();
        foreach($data as $k=>$v){
            if($k!=$this->primaryKey){
                $fields] = "$k=:$k";
                $d":$k"] = $v;
            }elseif(!empty($v)){
                $d":$k"] = $v;
            }

        }
        if(isset($data->$key) && !empty($data->$key)){
            $sql = 'UPDATE '.$this->table.' SET '.implode(',',$fields).' WHERE '.$key.'=:'.$key;
            $this->id = $data->$key;
            $action = 'update';
        } else{

            $sql = 'INSERT INTO '.$this->table.' SET '.implode(',',$fields);
            $action = 'insert';
        }
        $pre = $this->db->prepare($sql);
        $pre->execute($d);
        if($action == 'insert'){
            $this->id = $this->db->lastInsertId();

        }
    }

}

merci d’avance.