PDOStatement::setFetchMode()

(PHP 5 >= 5.1.0, PHP 7, PECL pdo >= 0.2.0)

为语句设置默认的获取模式。

说明

PDOStatement::setFetchMode(int $mode): bool

PDOStatement::setFetchMode(int$PDO::FETCH_COLUMN,int $colno): bool

PDOStatement::setFetchMode(int$PDO::FETCH_CLASS,string $classname,array $ctorargs): bool

PDOStatement::setFetchMode(int$PDO::FETCH_INTO,object $object): bool

参数

$mode

获取模式必须是PDO::FETCH_*系列常量中的一个。

$colno

列号。

$classname

类名。

$ctorargs

构造函数参数。

$object

对象。

返回值

成功时返回TRUE，或者在失败时返回FALSE。

范例

设置获取模式

The following example demonstrates how PDOStatement::setFetchMode() changes the default fetch mode for a PDOStatement object.下面的例子示范如何用PDOStatement::setFetchMode()来为一个 PDOStatement 对象更改默认的获取模式。

<?php
$sql = 'SELECT name, colour, calories FROM fruit';
try {
  $stmt = $dbh->query($sql);
  $result = $stmt->setFetchMode(PDO::FETCH_NUM);
  while ($row = $stmt->fetch()) {
    print $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\n";
  }
}
catch (PDOException $e) {
  print $e->getMessage();
}
?>

以上例程会输出：

apple   red     150
banana  yellow  250
orange  orange  300
kiwi    brown   75
lemon   yellow  25
pear    green   150
watermelon      pink    90

if you want to fetch your result into a class (by using PDO::FETCH_CLASS) and want the constructor to be executed *before* PDO assings the object properties, you need to use the PDO::FETCH_PROPS_LATE constant:
<?php
$stmt = $pdo->prepare("your query");
$stmt->setFetchMode(PDO::FETCH_CLASS|PDO::FETCH_PROPS_LATE, "className", $constructorArguments);
# pass parameters, if required by the query
$stmt->execute($parameters);
foreach ($stmt as $row)
{
  // do something with (each of) your object
}
?>

Something very helpful is knowing how to access namespaces from the function. It took me a minute (and Google) to figure out. The ::class property is going to be your best friend in this case.
<?php
$stmt->setFetchMode(PDO::FETCH_CLASS, Name\Space\Class::class);
?>

Some note on PDO :: FETCH_CLASS | PDO :: FETCH_CLASSTYPE
It took me some time, to realize, that you can not use this fetch-mode in $stm->setFetchMode(), when you want to retrieve objects from the database whereas the type is defined by the first column in the resultset.
You have to define this mode directly in the $stm->fetch() method.
To make it clearer:
$stm = $pdo->query("SELECT * FROM `foo`);
$stm->setFetchMode(FETCH_CLASS | PDO :: FETCH_CLASSTYPE);
$object = $stm->fetch();
Will not return the expected object, whereas
$stm = $pdo->query("SELECT * FROM `foo`");
$object = $stm->fetch(FETCH_CLASS | PDO :: FETCH_CLASSTYPE);
will give you the object of the class, defined in the first column of `foo`.

To fetch the rows into an existing instance of a class, use PDO::FETCH_INTO and pass the object as the second parameter. 
The class _must_ have the column names declared as public members, or the script will die. But overloading with __set() and __get() lets it handle any column your query throws at it. 
Set the fetch mode right after you call prepare(). It appears you _must_ use execute() - fetch() won't work. A small example, adapted from ext/pdo/tests/pdo_025.phpt:
<?php
class Test
{
  protected $cols;
  
  function __set($name, $value) {
    $this->cols[$name] = $value;
  }
  
  function __get($name) {
    return $this->cols[$name];
  }
}
$obj = new Test();
$db = PDOTest::factory();
$stmt = $db->prepare("select * from test");
$stmt->setFetchMode(PDO::FETCH_INTO, $obj);
$stmt->execute();
foreach ($stmt as $a) {
  print_r($a);
}
print_r($obj); // contains the same values as the last iteration above
?>

PDO::FETCH_CLASS may be used only with this method and it takes up to three parameters then:
 - int mode
 - string className
 - array constructorArgs (optional)
<?php
$stmt = $pdo -> query('your query');
$stmt -> setFetchMode(PDO::FETCH_CLASS, 'yourClass', array(0 => false));
while($row = $stmt -> fetch())
{
  // $row is an object of "yourClass" class
}
$stmt -> closeCursor();
?>
Note also that the constructor is called AFTER the data is set on the object.