markdown PDO和MySQL的基本CRUD操作
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# Basic CRUD operations with PDO
CRUD = Create, Read, Update, Delete
## Open a database connection
```php
$host = '127.0.0.1';
$dbname = 'test';
$username = 'root';
$password = '';
$charset = 'utf8';
$collate = 'utf8_unicode_ci';
$dsn = "mysql:host=$host;dbname=$dbname;charset=$charset";
$options = [
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_PERSISTENT => false,
PDO::ATTR_EMULATE_PREPARES => false,
PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES $charset COLLATE $collate"
];
$pdo = new PDO($dsn, $username, $password, $options);
```
## Select a single row
```php
$stmt = $pdo->prepare("SELECT * FROM users WHERE email = :email AND status=:status LIMIT 1");
$stmt->execute(['email' => $email, 'status' => $status]);
$user = $stmt->fetch();
```
## Select multiple rows
With fetch for large results.
```php
$stmt = $pdo->prepare("SELECT * FROM employees WHERE name = :name");
$stmt->execute(['name' => $name]);
foreach ($stmt as $row) {
// do something with $row
}
// or with the fech method:
while ($row = $stmt->fetch()) {
// do something with $row
}
```
With fetchAll for small results.
```php
$news = $pdo->query('SELECT * FROM news')->fetchAll();
```
## Insert a single row
```php
$row = [
'username' => 'bob',
'email' => 'bob@example.com'
];
$sql = "INSERT INTO users SET username=:username, email=:email;";
$status = $pdo->prepare($sql)->execute($row);
if ($status) {
$lastId = $pdo->lastInsertId();
echo $lastId;
}
```
## Insert multiple rows
```php
$rows = [];
$rows[] = [
'username' => 'bob',
'email' => 'bob@example.com'
];
$rows[] = [
'username' => 'max',
'email' => 'max@example.com'
];
$sql = "INSERT INTO users SET username=:username, email=:email;";
$stmt = $pdo->prepare($sql);
foreach ($rows as $row) {
$stmt->execute($row);
}
```
## Update a single row
```php
$row = [
'id' => 1,
'username' => 'bob',
'email' => 'bob2@example.com'
];
$sql = "UPDATE users SET username=:username, email=:email WHERE id=:id;";
$status = $pdo->prepare($sql)->execute($row);
```
## Update multiple rows
```php
$row = [
'updated_at' => '2017-01-01 00:00:00'
];
$sql = "UPDATE users SET updated_at=:updated_at";
$pdo->prepare($sql)->execute($row);
$affected = $pdo->rowCount();
```
## Delete a single row
```php
$where = ['id' => 1];
$pdo->prepare("DELETE FROM users WHERE id=:id")->execute($where);
```
## Delete multiple rows
```php
$pdo->prepare("DELETE FROM users")->execute();
```
## PDO datatypes
Getting dynamic (POST) data with null values can be difficult to handle with PDO.
Here is a helper function to detect the correct data type.
```php
function get_pdo_type($value)
{
switch (true) {
case is_bool($value):
$dataType = PDO::PARAM_BOOL;
break;
case is_int($value):
$dataType = PDO::PARAM_INT;
break;
case is_null($value):
$dataType = PDO::PARAM_NULL;
break;
default:
$dataType = PDO::PARAM_STR;
}
return $dataType;
}
// Usage
$email = $_POST['email'];
$pdo = new PDO('dsn', 'username', 'password');
$sql = 'INSERT INTO users SET email=:email;';
$stmt = $pdo->prepare($sql);
$stmt->bindValue(':email', $email, get_pdo_type($email));
$stmt->execute();
```
## Prepared statements using the IN clause
It cannot be done with PDO, according to the PHP Manual's entry on PDO::prepare(), which says:
"You cannot bind multiple values to a single named parameter in, for example, the IN() clause of an SQL statement."
This PDO helper function converts all array values into a (safe) quoted string.
```php
function quote_values(PDO $pdo, array $values) {
array_walk($values, function (&$value) use ($pdo) {
if($value === null) {
$value = 'NULL';
return;
}
$value = $pdo->quote($value);
});
return implode(',', $values);
}
```
Example usage:
```php
$ids = [
1,
2,
3,
"'",
null,
'string',
123.456
];
$sql = sprintf("SELECT id FROM users WHERE id IN(%s)", quote_values($pdo, $ids));
echo $sql . "\n";
$stmt = $pdo->prepare($sql);
$stmt->execute();
```
Generated SQL:
```sql
SELECT id FROM users WHERE id IN('1','2','3','\'',NULL,'string','123.456')
```
Other solutions:
* [PHP PDO Prepared Statements to Prevent SQL Injection](https://websitebeaver.com/php-pdo-prepared-statements-to-prevent-sql-injection#where-in-array)
* [Prepared statements and IN clause](https://phpdelusions.net/pdo#in)
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