把PDO方法库封装类的形式
<?php//PDOdb类封装Class MyDB{// 连接参数public $dsn;public $user;public $password;// 连接属性public $pdo;// 连接方法public function connect(){// 使用PDO方式管理数据库, 连接成功则返回PDO对象,赋值给对象属性pdo$this->pdo = new PDO($this->dsn, $this->user, $this->password);}// 希望在实例化时, 自动连接数据库, 这个需求很常见public function __construct($dsn, $user, $password){// 初始化对象属性$this->dsn = $dsn;$this->user = $user;$this->password = $password;// 自动调用对象方法,连接数据库$this->connect();}/*** 查询多条记录* @param $table* @param $fields* @param string $where* @return array*/public function select($table,$fields, $where='', $order='',$limit=''){//拼接SQL语句$sql = 'SELECT ';if (is_array($fields)) {foreach ($fields as $field) {$sql .= $field.', ';}} else {$sql .= $fields;}$sql = rtrim(trim($sql),',');$sql .= ' FROM '.$table;//查询条件if(!empty($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;}}/*** 查询单条记录* @param $table 表名* @param $fields 返回值 ** @param string $where 条件* @return array*/public function find($table,$fields,$where=''){$pdo = $this->pdo;//创建SQL语句$sql = 'SELECT ';if (is_array($fields)) {foreach ($fields as $field) {$sql .= $field.', ';}} else {$sql .= $fields;}$sql = rtrim(trim($sql),',');$sql .= ' FROM '.$table;//查询条件if(!empty($where)){$sql .= ' WHERE '.$where;}$sql .= ' LIMIT 1;';//创建PDO预处理对象$stmt = $pdo->prepare($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;}}/****添加数据*@param $table*@param $data*@return bool***/public function add($table,$data=[]){//创建SQL语句$sql = "INSERT INTO {$table} SET ";//组装插入语句if(is_array($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;}}/*** 更新数据* @param $table* @param $data* @return bool*/public function update($table,$data=[], $where='') {//创建SQL语句$sql = "UPDATE {$table} SET ";//组装修改语句if(is_array($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;}}/*** 删除数据* @param $db* @param $table* @param string $where* @return bool*/public function real_delete($table,$where=''){//创建SQL语句$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;}}/*** 统计数量* @param $pdo* @param $table* @param string $where* @return number*/public function count_num($table,$where=''){//创建SQL语句$sql = 'SELECT count(*) as count_number 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 $rows;}} else {return false;}}// 析构方法public function __destruct(){$this->pdo = null;}}// 实例化$mydb = new MyDB('mysql:host=localhost;dbname=php_2019', 'root', '******');if ($mydb->pdo) {echo '<h2>连接成功</h2>';}// // 读取数据库测试// $stmt = $db->pdo->prepare('select * from user');// $stmt->execute();// foreach ($stmt->fetchAll(PDO::FETCH_ASSOC) as $user) {// print_r($user); echo '<br>';// }echo '<h3>查询多条：</h3>';$res = $mydb->select('user','username');echo '<pre>';print_r($res);echo '<hr>';echo '<h3>查询一条：</h3>';$res = $mydb->find('user','username','uid=1');print_r($res);echo '<hr>';echo '<h3>添加数据：</h3>';$data = ['username' => 'xiaohong','password' => '123456',];$insert = $mydb->add('user',$data);var_dump($insert);echo '<hr>';echo '<h3>更新数据：</h3>';$data = ['password' => '111111',]; //这里密码的值不改，还是原来123456 居然执行结果会报null$update = $mydb->update('user',$data,'uid=4');var_dump($update);echo '<hr>';echo '<h3>删除数据：</h3>';$delete = $mydb->real_delete('user','uid=4');var_dump($delete);echo '<hr>';echo '<h3>统计：</h3>';$count = $mydb->count_num('user');echo $count;echo '<pre>';
运行截图：
总结：温故而知新，只要写了就会有收获。方法库改为类这个作业确实很简单，不会写的时候就是缺少那个思想。
