Introduction and use of PDO

1. PDO introduction

1.1 Link to the database

Method 1: mysql extension [php7 has been eliminated in this way]
Method 2: mysqli extension
Method 3: PDO extension

1.2 Introduction to PDO

The PDO (PHP Data Object) extension provides a lightweight and consistent interface for PHP to access various databases. No matter what database is accessed, it can be operated through a consistent interface.

1.2.1 Enable PDO extension

Open PDO connection MySQL extension

extension=php_pdo_mysql.dll

1.3 PDO core class

1. PDO class: indicates a connection between PHP and the database.
2. PDOStatement class.
First: indicates the relevant result set after executing the data query statement (select, show).
Second: preprocessing object
3. PDOException class: indicates PDO abnormal

1.4 instantiate PDO objects

grammar:

__construct($dsn, username, password)

1.4.1 DSN

DSN: data source name, the name of the data source, contains the information to connect to the database, the format is as follows:

$dsn=database type: host=host address; port=port number; dbname=database name; charset=charset

Database type:

MySQL database => mysql;
oracle database => oci;
SQL Server => sqlsrv; Please
refer to the manual "PDO Driver" for specific driver types

1.4.2 Instantiate PDO

The process of instantiating PDO is the process of connecting to the database.
Example:

<?php 
$dsn='mysql:host=localhost;port=3306;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');
var_dump($pdo);

effect:

1.4.3 Matters needing attention

1. If you are connecting to a local database, host can be omitted.

<?php 
$dsn='mysql:port=3306;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');
var_dump($pdo);

The effect is as above:

2. If the default port number is 3306, the port can also be omitted.

<?php 
$dsn='mysql:dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');
var_dump($pdo);

The effect is as above:

3. Charset is also omitted. If omitted, the default character encoding is used.

<?php 
$dsn='mysql:dbname=data;';
$pdo=new PDO($dsn, 'root', 'root');
var_dump($pdo);

The effect is as above:

4. dbname can also be omitted, if it is omitted, no database is selected:
Example:

<?php 
$dsn='mysql:';
$pdo=new PDO($dsn, 'root', 'root');
var_dump($pdo);

Effect:

5. The host, port, dbname, and charset are not case sensitive and there is no order.
example:

<?php 
$dsn='mysql:port=3306;host=localhost;dbName=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');
var_dump($pdo);

effect:

Two, use PDO

2.1 Executing data manipulation statements

Method: $pdo->exec($sql)Execute data addition, deletion, and modification statements, and return the number of affected records if the execution is successful, and return false if the SQL statement is wrong.

2.1.1, increase

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

//  2、执行数据增加操作语句 
if ($pdo->exec("insert into shows values (null, 'kk', 'kkkkk', CURRENT_TIMESTAMP)"))
    echo '自动增长的编号是：'.$pdo->lastInsertId(),'<br>';

effect:

2.1.2, change

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行修改
echo $pdo->exec('update shows set title="bb" where id=2');

effect:

2.1.3, delete

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行删除
echo $pdo->exec('delete from shows where id=2');

effect:

2.1.4. Check:

2.1.4.1, return a two-dimensional array

1. Return associative and indexed arrays

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
var_dump($stmt);
echo '<br>';
// 3、获取数据
// 3.1 获取二维数组
// $rs = $stmt->fetchAll(PDO::FETCH_BOTH) // 默认返回关联和索引
$rs = $stmt->fetchAll(PDO::FETCH_BOTH); // 返回关联和索引数组
echo '<pre>';
var_dump($rs);

effect:

---

2. Return the index array

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
var_dump($stmt);
echo '<br>';
// 3、获取数据
// 3.1 获取二维数组
// $rs = $stmt->fetchAll(PDO::FETCH_BOTH) // 默认返回关联和索引
$rs = $stmt->fetchAll(PDO::FETCH_NUM); // 返回索引数组
echo '<pre>';
var_dump($rs);

effect:

---

3. Return associative array

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
var_dump($stmt);
echo '<br>';
// 3、获取数据
// 3.1 获取二维数组
// $rs = $stmt->fetchAll() // 默认返回关联和索引
$rs = $stmt->fetchAll(PDO::FETCH_ASSOC); // 返回关联数组数组
echo '<pre>';
var_dump($rs);

effect:

---

4. Return an array of objects

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
var_dump($stmt);
echo '<br>';
// 3、获取数据
// 3.1 获取二维数组
// $rs = $stmt->fetchAll() // 默认返回关联和索引
$rs = $stmt->fetchAll(PDO::FETCH_OBJ); // 返回对象数组
echo '<pre>';
var_dump($rs);

effect:

---

2.1.4.2, return a one-dimensional array

1. Associative and indexed arrays are returned by default

Example:

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
var_dump($stmt);
echo '<br>';
// 3、获取数据
// 3.2 获取一维数组
$rs=$stmt->fetch(); // 默认返回关联和索引数组

echo '<pre>';
var_dump($rs);

effect:

---

2. Take the index array

Example:

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
var_dump($stmt);
echo '<br>';
// 3、获取数据
// 3.2 获取一维数组
$rs=$stmt->fetch(PDO::FETCH_NUM); // 默认返回索引数组,取一条，取完以后指针下移

echo '<pre>';
var_dump($rs);

effect:

---

3. Get all data through loop

Example:

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
var_dump($stmt);
echo '<br>';
// 3、获取数据
// 3.2 获取一维数组
while($row=$stmt->fetch(PDO::FETCH_ASSOC)) {
    
    
    $rs[]=$row;
}

echo '<pre>';
var_dump($rs);

effect:

---

2.1.4.3, animal sequence

Example:

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
// 3、获取数据
// 3.3 匹配列
echo $stmt->fetchColumn(); // 默认获取当前行的第0列
// echo $stmt->fetchColumn(1); // 获取当前行第一列
echo '<pre>';

effect:

---

2.1.4.4, matching total number of rows, total number of columns

Example:

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');
// 3、获取数据
// 3.4 总行数、总列数
echo '总行数：'.$stmt->rowCount(),'<br>';
echo '总列数：'.$stmt->columnCount(),'<br>';

effect:

---

Three, traverse PDOStatement

Example:

<?php 
// 1、实例化PDO
$dsn='mysql:port=3306;host=localhost;dbname=data;charset=utf8';
$pdo=new PDO($dsn, 'root', 'root');

// 2、执行查询
$stmt = $pdo->query('select * from shows');

// PDOStatement对象中是有迭代器的
foreach($stmt as $row) {
    
    
    echo $row['id'],'-',$row['title'],$row['content'],'-',$row['createTime'];
    echo '<br>';
}

effect:

---

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