问题描述
我的 Web 应用程序目前确实执行了简单的查询:简单的 CRUD 操作、计数、...
My web application currently has do execute simple queries: simple CRUD operations, counting,...
几个月前，有人推荐我在这里为此编写一个简单的 PDO 包装器(以避免每次应执行查询时编写 try/catch、prepare()、execute() 等).显示了此示例方法(我进行了一些更改，以便可以在我自己的项目中使用它):
A few months ago, someone recommended me here to write a simple PDO wrapper for this (to avoid writing try/catch, prepare(), execute(), etc. each time a query should be executed). This example method was shown (I've made some changes so I could use it in my own project):
public function execute() {
$args = func_get_args();
$query = array_shift($args);
$result = false;
try {
$res = $this->pdo->prepare($query);
$result = $res->execute($args);
} catch (PDOException $e) { echo $e->getMessage(); }
return $result;
}
由于我需要执行更多操作(执行查询、检索 1 条记录、检索多条记录、计算结果)，我为所有这些操作创建了一个方法:
As I need to perform more operations (executing queries, retrieving 1 record, retrieving multiple records, counting results) I created a method for all of these:
public function getMultipleRecords() {
$args = func_get_args();
$query = array_shift($args);
$records = array();
try {
$res = $this->pdo->prepare($query);
$res->execute($args);
$records = $res->fetchAll();
} catch (PDOException $e) { echo $e->getMessage(); }
return $records;
}
public function getSingleRecord() {
$args = func_get_args();
$query = array_shift($args);
$record = array();
try {
$res = $this->pdo->prepare($query);
$res->execute($args);
$record = $res->fetch();
} catch (PDOException $e) { echo $e->getMessage(); }
return $record;
}
public function execute() {
$args = func_get_args();
$query = array_shift($args);
$result = false;
try {
$res = $this->pdo->prepare($query);
$result = $res->execute($args);
} catch (PDOException $e) { echo $e->getMessage(); }
return $result;
}
public function count() {
$args = func_get_args();
$query = array_shift($args);
$result = -1;
try {
$res = $this->pdo->prepare($query);
$res->execute($args);
$result = $res->fetchColumn();
} catch(PDOException $e) { echo $e->getMessage(); }
return $result;
}
如您所见，大部分代码是相同的.每种方法只有 2 行代码不同:$result 的初始化(我总是想返回一个值，即使查询失败)和获取.我可以不使用 4 种方法，而是只编写其中一种并传递一个带有操作类型的额外参数.这样，我可以使用 switch 语句的一堆 if/else 语句.但是，我认为代码可能会变得混乱.这是解决这个问题的好方法吗?如果没有，有什么好的解决办法?
As you see, most of the code is the same. Only 2 lines of code are different for each method: the initialisation of $result (I always want to return a value, even if the query fails) and the fetching. Instead of using 4 methods, I could write just one of them and pass an extra parameter with the type of action. That way, I could use a bunch of if/else statements of a switch statement. However, I think the code can get messy. Is this a good way for solving this problem? If not, what would be a good solution to it?
我遇到的第二个问题(这就是我现在正在研究这个类的原因)是我想将准备好的语句与 LIMIT SQL 语句一起使用.但是，这是不可能的:
The second problem I have (which is why I'm working on this class right now) is that I want to use prepared statements with the LIMIT SQL statement. However, it is not possible to do this:
$res = $pdo->prepare("SELECT * FROM table LIMIT ?");
$res->execute(array($int));
由于某种原因，变量将被引用(因此查询将失败)，如下所述:https://bugs.php.net/bug.php?id=40740
The variabele will be quoted for some reason (and so the query will fail), as explained here: https://bugs.php.net/bug.php?id=40740
解决方案似乎使用 bindValue() 并使用 int 数据类型作为参数:http://www.php.net/manual/de/pdostatement.bindvalue.php
The solution seems to use bindValue() and use the int datatype as a parameter: http://www.php.net/manual/de/pdostatement.bindvalue.php
我可以重写方法来支持这一点，但我还需要使用一个额外的参数.我不能再使用 $db->execute($sql, $variable1, $variable2); 因为我需要知道数据类型.
I could rewrite the method(s) to support this, but I would also need to use an extra parameter. I can't just use $db->execute($sql, $variable1, $variable2); anymore as I need to know the data type.
解决这个问题的最佳方法是什么?
What's the best way to solve this?
谢谢
推荐答案
如何使用可以链接的方法创建一个类(为了清楚起见，我已经删除了错误检查):
How about creating a class with methods that you can chain (for clarity, I've removed error checking):
class DB {
private $dbh;
private $stmt;
public function __construct($user, $pass, $dbname) {
$this->dbh = new PDO(
"mysql:host=localhost;dbname=$dbname",
$user,
$pass,
array( PDO::ATTR_PERSISTENT => true )
);
}
public function query($query) {
$this->stmt = $this->dbh->prepare($query);
return $this;
}
public function bind($pos, $value, $type = null) {
if( is_null($type) ) {
switch( true ) {
case is_int($value):
$type = PDO::PARAM_INT;
break;
case is_bool($value):
$type = PDO::PARAM_BOOL;
break;
case is_null($value):
$type = PDO::PARAM_NULL;
break;
default:
$type = PDO::PARAM_STR;
}
}
$this->stmt->bindValue($pos, $value, $type);
return $this;
}
public function execute() {
return $this->stmt->execute();
}
public function resultset() {
$this->execute();
return $this->stmt->fetchAll();
}
public function single() {
$this->execute();
return $this->stmt->fetch();
}
}
然后您可以像这样使用它:
You can then use it like this:
// Establish a connection.
$db = new DB('user', 'password', 'database');
// Create query, bind values and return a single row.
$row = $db->query('SELECT col1, col2, col3 FROM mytable WHERE id > ? LIMIT ?')
->bind(1, 2)
->bind(2, 1)
->single();
// Update the LIMIT and get a resultset.
$db->bind(2,2);
$rs = $db->resultset();
// Create a new query, bind values and return a resultset.
$rs = $db->query('SELECT col1, col2, col3 FROM mytable WHERE col2 = ?')
->bind(1, 'abc')
->resultset();
// Update WHERE clause and return a resultset.
$db->bind(1, 'def');
$rs = $db->resultset();
如果您愿意，您可以更改 bind 方法以接受数组或关联数组，但我发现此语法非常清晰 - 它避免了必须构建数组.参数类型检查是可选的，因为 PDO::PARAM_STR 适用于大多数值，但请注意传递空值时的潜在问题(请参阅 PDOStatement->bindValue 文档中的注释).
You could alter the bind method to accept an array or associative array if you prefer, but I find this syntax quite clear - it avoids having to build an array. The parameter type checking is optional, as PDO::PARAM_STR works for most values, but be aware of potential issues when passing null values (see comment in PDOStatement->bindValue documentation).
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