php class类 PDO 增删查改

<?php
class NB{
    function __construct($a,$b,$c,$table)
    {
        //pdo连接数据库
        $this->pdo = new PDO($a,$b,$c);
        //需要增删查改的表明
        $this->table = $table;
    }
    //查询
    function select($where = '', $limit = 6){
        $where = empty($where) ? '' : ' WHERE '.$where;
        $limit = ' LIMIT ' . $limit;
        $sql = 'SELECT * FROM ' .$this->table. $where . $limit;
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute();
        return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }
    //新增
    function insert($data){
        //数据表字段列表
        $a = '(name,tel,password) ';
        //字段值列表
        $b = '(:name,:tel,:password)';
        //创建sql语句模板
        $sql = 'INSERT INTO ' . $this->table . $a .' VALUES' .$b;
        //预处理新增操作
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($data);
        //返回新增数量，及其主键id
        return [
            'count' => $stmt->rowCount(),
            'id' => $this->pdo->lastInsertId()
        ];
    }
    //更新
    function update($upda,$upid){
        //通过外部数组索引数组
        $keyArr = array_keys($upda);
        $set = '';
        //循环外部索引数组，获得如name=:name
        foreach($keyArr as $vv){
            // .=能让 $set 获取所有数组，若只有 = ，则只能获取只有一个数组
            $set .= $vv . '=:'.$vv . ', ';
        }
        $set = rtrim($set, ', ');
        echo $set;
        $sql = 'UPDATE '.$this->table.' SET '.$set.' WHERE ' .$upid;
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute($upda);
        return $stmt->rowCount();
    }
    //删除
    function delete($deid){
        $sql = 'DELECT FROM '.$this->table.' WHERE '. $deid;
        $stmt = $this->pdo->prepare($sql);
        $stmt->execute();
        return $stmt->rowCount();
    }
}
$db = new NB('mysql:host=localhost;dbname=film', 'root', 'root', 'user');
echo print_r($db->pdo);
echo '<hr>';

//查询结果
foreach($db->select() as $v){
    print_r($v);
}
echo '<hr>';

//新增
$data = [
    'name'=> '轩轩宝贝',
    'tel'=>211899,
    'password'=>sha1(123456)
];
$inss = $db->insert($data);
echo '成功新增'.$inss['count'].'，它的主键id：'. $inss['id'];
echo '<hr>';

//更新
$upda = [
    'name' => '轩轩宝贝',
    'tel'=> 15566554466
];
$upid = 'id=14';
echo '成功更新了' . $db->update($upda,$upid).'条信息';
echo '<hr>';

//删除
$deid = 'id=12';
echo '成功删除：' .$db->delete($deid). '条信息';