封装简单的数据库操作类

需要封装数据库操作类，先看看我们需要哪些准备。

1.我们要了解sql语句的结构

2.要知道什么是连贯操作

3.关于占位符的使用，目的是为了让连贯操作打乱顺续不影响sql语句的生成

下面是步骤，先封装需要用到的属性

Class Model
{
    protected $host;//主机名
    protected $user;//用户名
    protected $password;//密码
    protected $dbname;//数据库名
    protected $charset;//字符集
    protected $prefix;//数据表前缀

    //数据库连接资源
    protected $link;
    //表名
    protected $tableName;
    //操作数组
    protected $options;

然后写构造函数来初始化属性，这当中的$link调用一个connect（）方法，$tableName调用getTableName方法，并调用initOptions方法将操作数组初始化。

//构造方法
    public function __construct($config)
    {
        $this->host = $config['DB_HOST'];
        $this->user = $config['DB_USER'];
        $this->password = $config['DB_PWD'];
        $this->dbname = $config['DB_NAME'];
        $this->charset = $config['DB_CHARSET'];
        $this->prefix = $config['DB_PREFIX'];
        $this->link = $this->connect();
        $this->tableName = $this->getTableName();
        //初始化操作数组
        $this->initOptions();
    }

connect（）方法

protected function connect()
    {
        //连接数据库
        $link = mysqli_connect($this->host, $this->user, $this->password, $this->dbname);
        if (!$link) {
            die('数据库连接失败');
        }
        //设置字符集
        mysqli_set_charset($link, $this->charset);
        return $link;
    }

getTableName()

protected function getTableName()
    {
        if (!empty($this->tableName)) {
            $tableName = $this->prefix . $this->tableName;
        } else {
            $className = get_class($this);
            $table = strtolower(substr($className, 0, -5));
            $tableName = $this->prefix . $table;
        }
        return $tableName;
    }

initOptions()方法

protected function initOptions()
    {
        $arr = ['where', 'table', 'field', 'group', 'order', 'having', 'limit'];
        foreach ($arr as $value) {
            $this->options[$value] = '';
        }
        if ($value == 'table') {
            $this->options[$value] = $this->tableName;
        }
    }

然后是操作的函数，用来拼接sql语句。

 //field
    function field($field)
    {
        if (!empty($field)) {
            if (is_string($field)) {
                $this->options['field'] = $field;
            } else if (is_array($field)) {
                $this->options['field'] = join(',', $field);
            }
        }
        return $this;
    }

    //table
    function table($table)
    {
        if (!empty($table)) {
            $this->options['table'] = $table;
        }
        return $this;
    }

    //where
    function where($where)
    {
        if (!empty($where)) {
            $this->options['where'] = 'where ' . $where;
        }
        return $this;
    }

    //group
    function group($group)
    {
        if (!empty($group)) {
            $this->options['group'] = 'group by' . $group;
        }
        return $this;
    }

    //having
    function having($having)
    {
        if (!empty($having)) {
            $this->options['having'] = 'having' . $having;
        }
        return $this;
    }

    //order
    function order($order)
    {
        if (!empty($order)) {
            $this->options['order'] = 'order by' . $order;
        }
        return $this;
    }

    //limit
    function limit($limit)
    {
        if (!empty($limit)) {
            if (is_string($limit)) {
                $this->options['limit'] = 'limit ' . $limit;
            } else if (is_array($limit)) {
                $this->options['limit'] = 'limit ' . join(',', $limit);
            }
            return $this;
        }
    }

最后写上我们的增删改查的函数即可。

 //select
    function select()
    {
        $sql = 'select %FIELD% from %TABLE% %WHERE% %GROUP% %HAVING% %ORDER% %LIMIT%';
        $sql = str_replace(['%FIELD%', '%TABLE%', '%WHERE%', '%GROUP%', '%HAVING%', '%ORDER%', '%LIMIT%'],
            [$this->options['field'], $this->options['table'], $this->options['where'], $this->options['group'], $this->options['having'], $this->options['order'], $this->options['limit']], $sql);

        $this->sql = $sql;
        //执行sql
        return $this->query($sql);
    }

    //query
    function query($sql)
    {   $this->initOptions();
        /*var_dump($sql);
        die();*/

        $result = mysqli_query($this->link, $sql);
        while ($row = mysqli_fetch_assoc($result)) {
            $newRow[] = $row;
        }
        return $newRow;

    }

    function insert($data)
    {
        //读数组进行处理
        $data = $this->changeData($data);
        $keys = array_keys($data);
        $values = array_values($data);
        $sql = 'insert into %TABLE% (%FIELD%) VALUES (%VALUES%)';
        $sql = str_replace(['%TABLE%', '%FIELD%', '%VALUES%'], [$this->options['table'], join(',', $keys), join(',', $values)], $sql);
        $this->sql = $sql;
        return $this->exec($sql, true);
    }

    function delete()
    {
        $sql = 'delete from %TABLE% %WHERE%';
        $sql = str_replace(['%TABLE%', '%WHERE%'],
            [$this->options['table'], $this->options['where']], $sql);
        $this->sql = $sql;
        return $this->exec($sql,false);
    }

    function update($data){
        $data=$this->changeData($data);
        $value=$this->changeUpdate($data);
        $sql = 'update  %TABLE% set %VALUE% %WHERE%';
        $sql = str_replace(['%TABLE%','%VALUE%', '%WHERE%'],
            [$this->options['table'],$value, $this->options['where']], $sql);
        $this->sql = $sql;
        return $this->exec($sql,false);
      }

    //exec
    function exec($sql, $isInsert)
    {   $this->initOptions();
        $result = mysqli_query($this->link, $sql);
        if ($isInsert) {
            return mysqli_insert_id($this->link);
        } else {
            return mysqli_affected_rows($this->link);
        }
    }
    //更新函数数据源格式
    function changeUpdate($data){
        foreach($data as $key=>$value){
            $newdata[]=$key.'='.$value;
        }return join(',',$newdata);
    }
    //添加数据数据源更改
    function changeData($data)
    {
        foreach ($data as $key => $value) {
            if (is_string($value)) {
                $value = '"' . $value . '"';
            }
            $newData[$key] = $value;
        }
        return $newData;
    }

    function __get($name)
    {
        if ($name == 'sql') {
            return $this->sql;
        }
        return false;

    }