023-11月27日-PHP第13节-类自动加载、继承

1. 把 php公用方法库中的 数据库操作函数， 重写到 Db类中。

class DB{
        public $dsn;
        public $user;
        public $password;
        public $pdo;
        public $table;
//        public $table;
//        public $fields;
//        public $where;
//        public $order;
//        public $limit;
//        public $stmt;
        public function __construct($dsn,$user,$password,$table)
        {
            $this->dsn = $dsn;
            $this->user = $user;
            $this->password = $password;
            $this->table = $table;
            $this->connect();
            //已经预处理，后面函数不用添加此语句了
        }
        public function connect(){
            $this->pdo = new PDO($this->dsn,$this->user,$this->password);
        }
        public function select($fields, $where='', $order='',$limit=''){
//            $this->table = $table;
            $sql = 'SELECT ';
            if (is_array($fields)) {
                foreach ($fields as $field) {
                    $sql .= $field.', ';
                }
            } else {
                $sql .= $fields;
            }
            $sql = rtrim(trim($sql),',');
            $sql .= '  FROM '.$this->table;
            //查询条件
            if(!empty($where)){
                $sql .= ' WHERE '.$where;
            }
            //排序条件
            if(!empty($order)) {
                $sql .= ' order by '.$order;
            }
            //分页条件
            if(!empty($limit)) {
                $sql .= ' limit '.$limit;
            }
            $sql .= ';';
            //创建PDO预处理对象
            $stmt = $this->pdo->prepare($sql);
            //执行查询操作
            if($stmt->execute()){
                if($stmt->rowCount()>0){
                    $stmt->setFetchMode(PDO::FETCH_ASSOC);
                    //返回一个二维数组
                    return $stmt->fetchAll();
                }
            } else {
                return false;
            }
        }
        public function find($fields,$where=''){
            $sql = 'SELECT ';
            if (is_array($fields)) {
                foreach ($fields as $field) {
                    $sql .= $field.', ';
                }
            } else {
                $sql .= $fields;
            }
            $sql = rtrim(trim($sql),',');
            $sql .= ' FROM '.$this->table;
            //查询条件
            if(!empty($where)){
                $sql .= ' WHERE '.$where;
            }
            $sql .= ' LIMIT 1;';
            //创建PDO预处理对象
            $stmt = $this->pdo->prepare($sql);
            //执行查询操作
            if($stmt->execute()){
                if($stmt->rowCount()>0){
                    $stmt->setFetchMode(PDO::FETCH_ASSOC);
                    return $stmt->fetch();
                }
            } else {
                return false;
            }
        }
        public function insert($data=[]){
            $sql = "INSERT INTO {$this->table} SET ";
            //组装插入语句
            if(is_array($data)){
                foreach ($data as $k=>$v) {
                    $sql .= $k.'="'.$v.'", ';
                }
            }else{
                return false;
            }
            //去掉尾部逗号,并添加分号结束
            $sql = rtrim(trim($sql),',').';';
            //创建PDO预处理对象
            $stmt = $this->pdo->prepare($sql);
            //执行新增操作
            if($stmt->execute()){
                if($stmt->rowCount()>0){
                    return true;
                }
            } else {
                return false;
            }
        }
        public function update($data=[], $where=''){
            $sql = "UPDATE {$this->table} SET ";
            //组装修改语句
            if(is_array($data)){
                foreach ($data as $k=>$v) {
                    $sql .= $k.'="'.$v.'", ';
                }
            }
            //去掉尾部逗号,并添加分号结束
            $sql = rtrim(trim($sql),',');
            //查询条件
            if(!empty($where)){
                $sql .= ' WHERE '.$where;
            }
            //创建PDO预处理对象
            $stmt = $this->pdo->prepare($sql);
            //执行新增操作
            if($stmt->execute()){
                if($stmt->rowCount()>0){
                    return true;
                }
            } else {
                return false;
            }
                }
        public function delete($where=''){
            $sql = "DELETE FROM {$table}  ";
            //查询条件
            if(!empty($where)){
                $sql .= ' WHERE '.$where;
            }
            //创建PDO预处理对象
            $stmt = $this->pdo->prepare($sql);
            //执行删除操作
            if($stmt->execute()){
                if($stmt->rowCount()>0){
                    return true;
                }
            } else {
                return false;
            }
        }
        public function count_num($where){
            $sql  = 'SELECT count(*) as count_number FROM '.$this->table;
            //查询条件
            if(!empty($where)){
                $sql .= ' WHERE '.$where;
            }
            //创建PDO预处理对象
            $stmt = $this->pdo->prepare($sql);
            //执行查询操作
            if($stmt->execute()){
                if($stmt->rowCount()>0){
                    $row  = $stmt->fetch(PDO::FETCH_ASSOC);
                    $rows = $row['count_number'];
                    return $rows;
                }
            } else {
                return false;
            }
        }
    }
    $db = new DB('mysql:host=localhost;dbname=anguoguo','root','root','movies');
    //连接pdo
    print_r($db);
    $result1 = $db->select('name','cate_id=2','mov_id DESC');
    print_r($result1);
    //echo是输出类型--Array,结果集用print_r输出
    echo '<hr/>';
    $result2 = $db->find('image,name','mov_id=5');
    print_r($result2);
    echo '<hr/>';
    $array3 =[
        'mov_id' =>10,
        'name' =>'插入',
        'image'=>'10.jpg',
        'detail'=>'能否插入成功',
        'cate_id'=>'4'
    ];
    $result3 = $db->insert($array3);
    //插入是否有问题--当为数组时，不用加‘’，返回值插入成功--1
    print_r($result3);
    echo '<hr/>';
    $result4 = $db->update('[image=>10.jpg]','mov_id=5');
    print_r($result4);
    echo '<hr/>';
    $result5 = $db->delete('');
    print_r($result5);
    echo '<hr/>';
    $result6 = $db->count_num('mov_id');
    print_r($result6);
    echo '<hr/>';

另外

类名不区分大小写，函数名区分
构造方法是预处理，不是一定输出