How to write your own database package (2)

Connector.php

• Responsible for communicating with the database, adding, deleting, modifying and reading (CRUD)

First, create a Connector class, and set the attribute

<?php
class Connector {
    // 数据库地址前缀，常见的有mysql，slqlsrv，odbc等等等
    private $driver = &#39;mysql&#39;;
    // 数据库地址
    private $host = &#39;localhost&#39;;
    // 数据库默认名称, 设置为静态是因为有切换数据库的需求
    private static $db = &#39;sakila&#39;;
    // 数据库用户名
    private $username = &#39;root&#39;;
    // 数据库密码
    private $password = &#39;&#39;;
    // 当前数据库连接
    protected $connection;
    // 数据库连接箱，切换已存在的数据库连接不需要重新通信，从这里取即可
    protected static $container = [];

    // PDO默认属性配置，具体请自行查看文档
    protected $options = [
        PDO::ATTR_CASE => PDO::CASE_NATURAL,
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_ORACLE_NULLS => PDO::NULL_NATURAL,
        PDO::ATTR_STRINGIFY_FETCHES => false,
    ];
}

The above code should be understandable with comments , so I won’t explain it further and go directly to the function

• buildConnectString - is to generate a DSN connection string, very straightforward

    protected function buildConnectString() {
        return "$this->driver:host=$this->host;dbname=".self::$db;
    }
        // "mysql:host=localhost;dbname=sakila;"

• connect - Connect to the database

    public function connect() {
        try {
            // 连接数据库，生成pdo实例， 将之赋予$connection，并存入$container之中
            self::$container[self::$db] = $this->connection = new PDO($this->buildConnectString(), $this->username, $this->password, $this->options);
            // 返回数据库连接
            return $this->connection;
        } catch (Exception $e) {
            // 若是失败, 返回原因
            // 还记得dd()吗?这个辅助函数还会一直用上
            dd($e->getMessage());
        }
    }

• setDatabase - Switch database

    public function setDatabase($db) {
        self::$db = $db;
        return $this;
    }

• _construct - What is the first step after generating an instance

    function construct() {
        // 如果从未连接过该数据库, 那就新建连接
        if(empty(self::$container[self::$db])) $this->connect();
        // 反之, 从$container中提取, 无需再次通信
        $this->connection = self::$container[self::$db];
    }

The next two functional expressions are used together. You may be confused by looking at them alone. Step by step with the exampleDebugging

$a = new Connector();

$bindValues = [
    'PENELOPE',
    'GUINESS'
];

dd($a->read('select * from actor where first_name = ? and last_name = ?', $bindValues));

Return value

array (size=1)
  0 => 
    object(stdClass)[4]
      public 'actor_id' => string '1' (length=1)
      public 'first_name' => string 'PENELOPE' (length=8)
      public 'last_name' => string 'GUINESS' (length=7)
      public 'last_update' => string '2006-02-15 04:34:33' (length=19)

• read - read data

    public function read($sql, $bindings) {
        // 将sql语句放入预处理函数
        // $sql = select * from actor where first_name = ? and last_name = ?
        $statement = $this->connection->prepare($sql);
        // 将附带参数带入pdo实例
        // $bindings = ['PENELOPE', 'GUINESS']
        $this->bindValues($statement, $bindings);
        // 执行
        $statement->execute();
        // 返回所有合法数据, 以Object对象为数据类型
        return $statement->fetchAll(PDO::FETCH_OBJ);
    }

• bindValues ​​- bring the attached parameters into the pdo instance

        // 从例子中可以看出, 我用在预处理的变量为?, 这是因为pdo的局限性, 有兴趣可以在评论区讨论这个问题
    public function bindValues($statement, $bindings) {
        // $bindings = ['PENELOPE', 'GUINESS']
        // 依次循环每一个参数
        foreach ($bindings as $key => $value) {
            // $key = 0/1
            // $value = 'PENELOPE'/'GUINESS'
            $statement->bindValue(
                // 如果是字符串类型, 那就直接使用, 反之是数字, 将其+1
                // 这里是数值, 因此返回1/2
                is_string($key) ? $key : $key + 1,
                // 直接放入值
                // 'PENELOPE'/'GUINESS'
                $value,
                // 这里直白不多说
                // PDO::PARAM_STR/PDO::PARAM_STR
                is_int($value) ? PDO::PARAM_INT : PDO::PARAM_STR
            );
        }
    }

  So do you understand _( :3　∠)

• #update - Rewrite data

    // 与read不同的地方在于, read返回数据, update返回boolean(true/false)
    public function update($sql, $bindings) {
        $statement = $this->connection->prepare($sql);
        $this->bindValues($statement, $bindings);
        return $statement->execute();
    }

• delete - Delete data

  // 与update一样, 分开是因为方便日后维护制定
    public function delete($sql, $bindings) {
        $statement = $this->connection->prepare($sql);
        $this->bindValues($statement, $bindings);
        return $statement->execute();
    }

• create - Add data

  // 返回最新的自增ID, 如果有
    public function create($sql, $bindings) {
        $statement = $this->connection->prepare($sql);
        $this->bindValues($statement, $bindings);
        $statement->execute();
        return $this->lastInsertId();
    }

• lastInsertId - Return

  Add id, if any

    // pdo自带,只是稍微封装
    public function lastInsertId() {
        $id = $this->connection->lastInsertId();
        return empty($id) ? null : $id;
    }

Too advanced and complex SQL statements may not be encapsulated, so we have prepared two functions that can directly communicate with the database using RAW query

##exec - Suitable for additions, deletions and modifications

•   public function exec($sql) {
        return $this->connection->exec($sql);
    }

query - Suitable for reading

•   public function query($sql) {
        $q = $this->connection->query($sql);
        return $q->fetchAll(PDO::FETCH_OBJ);
    }

Encapsulates functions related to database transactions, straightforward so there are no comments

        public function beginTransaction() {
        $this->connection->beginTransaction();
        return $this;
    }

    public function rollBack() {
        $this->connection->rollBack();
        return $this;
    }

    public function commit() {
        $this->connection->commit();
        return $this;
    }

    public function inTransaction() {
        return $this->connection->inTransaction();
    }

Complete code

<?php
class Connector {
    // 数据库地址前缀，常见的有mysql，slqlsrv，odbc等等等
    private $driver = &#39;mysql&#39;;
    // 数据库地址
    private $host = &#39;localhost&#39;;
    // 数据库默认名称, 设置为静态是因为有切换数据库的需求
    private static $db = &#39;sakila&#39;;
    // 数据库用户名
    private $username = &#39;root&#39;;
    // 数据库密码
    private $password = &#39;&#39;;
    // 当前数据库连接
    protected $connection;
    // 数据库连接箱，切换已存在的数据库连接不需要重新通信，从这里取即可
    protected static $container = [];

    // PDO默认属性配置，具体请自行查看文档
    protected $options = [
        PDO::ATTR_CASE => PDO::CASE_NATURAL,
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_ORACLE_NULLS => PDO::NULL_NATURAL,
        PDO::ATTR_STRINGIFY_FETCHES => false,
    ];

    function construct() {
        // 如果从未连接过该数据库, 那就新建连接
        if(empty(self::$container[self::$db])) $this->connect();
        // 反之, 从$container中提取, 无需再次通信
        $this->connection = self::$container[self::$db];
    }

    // 生成DSN连接串
    protected function buildConnectString() {
        return "$this->driver:host=$this->host;dbname=".self::$db;
    }

    // 连接数据库
    public function connect() {
        try {
            // 连接数据库，生成pdo实例， 将之赋予$connection，并存入$container之中
            self::$container[self::$db] = $this->connection = new PDO($this->buildConnectString(), $this->username, $this->password, $this->options);

            // 返回数据库连接
            return $this->connection;
        } catch (Exception $e) {
            // 若是失败, 返回原因
            dd($e->getMessage());
        }
    }

    // 切换数据库
    public function setDatabase($db) {
        self::$db = $db;
        return $this;
    }

    // 读取数据
    public function read($sql, $bindings) {
        // 将sql语句放入预处理函数
        $statement = $this->connection->prepare($sql);
        // 将附带参数带入pdo实例
        $this->bindValues($statement, $bindings);
        // 执行
        $statement->execute();
        // 返回所有合法数据, 以Object对象为数据类型
        return $statement->fetchAll(PDO::FETCH_OBJ);
    }

    // 将附带参数带入pdo实例
    public function bindValues($statement, $bindings) {
        // 依次循环每一个参数
        foreach ($bindings as $key => $value) {
            $statement->bindValue(
                // 如果是字符串类型, 那就直接使用, 反之是数字, 将其+1
                is_string($key) ? $key : $key + 1,
                // 直接放入值
                $value,
                // 这里直白不多说
                is_int($value) ? PDO::PARAM_INT : PDO::PARAM_STR
            );
        }
    }

    // 改写数据
    public function update($sql, $bindings) {
        // 与read不同的地方在于, read返回数据, update返回boolean(true/false)
        $statement = $this->connection->prepare($sql);
        $this->bindValues($statement, $bindings);
        return $statement->execute();
    }

    // 删除数据
    public function delete($sql, $bindings) {
        $statement = $this->connection->prepare($sql);
        $this->bindValues($statement, $bindings);
        return $statement->execute();
    }

    // 增加数据
    public function create($sql, $bindings) {
        $statement = $this->connection->prepare($sql);
        $this->bindValues($statement, $bindings);
        $statement->execute();
        return $this->lastInsertId();
    }

    // 返回新增id, 如果有
    public function lastInsertId() {
        $id = $this->connection->lastInsertId();
        return empty($id) ? null : $id;
    }

    // 适用于增删改
    public function exec($sql) {
        return $this->connection->exec($sql);
    }

    // 适用于读
    public function query($sql) {
        $q = $this->connection->query($sql);
        return $q->fetchAll(PDO::FETCH_OBJ);
    }

    public function beginTransaction() {
        $this->connection->beginTransaction();
        return $this;
    }

    public function rollBack() {
        $this->connection->rollBack();
        return $this;
    }

    public function commit() {
        $this->connection->commit();
        return $this;
    }

    public function inTransaction() {
        return $this->connection->inTransaction();
    }
}

Questions in this issue

1.) Due to the characteristics of PHP itself, by default all code classes will be destructed after running, and pdo will automatically break connection, so I did not disconnect() and let pdo disconnect. I wonder if this is a bad practice?

2.) The two functions of adding and rewriting data do not support adding multiple sets of data at one time. This is a one-time addition. The reason is that I deleted it because I thought it was too cumbersome. If you are interested, you can provide a solution

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