PDOStatement::fetchAll

(PHP 5 >= 5.1.0, PHP 7, PHP 8, PECL pdo >= 0.1.0)

PDOStatement::fetchAll — 返回一个包含结果集中所有行的数组

说明

PDOStatement::fetchAll ( int $fetch_style = ? , mixed $fetch_argument = ? , array $ctor_args = array() ) : array

参数

fetch_style

控制返回数组的内容如同 PDOStatement::fetch() 文档中记载的一样。默认为 PDO::ATTR_DEFAULT_FETCH_MODE 的值（ 其缺省值为 PDO::FETCH_BOTH ）

想要返回一个包含结果集中单独一列所有值的数组，需要指定 PDO::FETCH_COLUMN 。通过指定 column-index 参数获取想要的列。

想要获取结果集中单独一列的唯一值，需要将 PDO::FETCH_COLUMN 和 PDO::FETCH_UNIQUE 按位或。

想要返回一个根据指定列把值分组后的关联数组，需要将 PDO::FETCH_COLUMN 和 PDO::FETCH_GROUP 按位或。

fetch_argument

根据 fetch_style 参数的值，此参数有不同的意义：

  • PDO::FETCH_COLUMN：返回指定以0开始索引的列。

  • PDO::FETCH_CLASS：返回指定类的实例，映射每行的列到类中对应的属性名。

  • PDO::FETCH_FUNC：将每行的列作为参数传递给指定的函数，并返回调用函数后的结果。

ctor_args

当 fetch_style 参数为 PDO::FETCH_CLASS 时，自定义类的构造函数的参数。

返回值

PDOStatement::fetchAll() 返回一个包含结果集中所有剩余行的数组。此数组的每一行要么是一个列值的数组，要么是属性对应每个列名的一个对象。

使用此方法获取大结果集将导致系统负担加重且可能占用大量网络资源。与其取回所有数据后用PHP来操作，倒不如考虑使用数据库服务来处理结果集。例如，在取回数据并通过PHP处理前，在 SQL 中使用 WHERE 和 ORDER BY 子句来限定结果。

范例

Example #1 获取结果集中所有剩余的行

<?php
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();

/* 获取结果集中所有剩余的行 */
print("Fetch all of the remaining rows in the result set:\n");
$result = $sth->fetchAll();
print_r($result);
?>

以上例程的输出类似于：

Fetch all of the remaining rows in the result set:
Array
(
    [0] => Array
        (
            [NAME] => pear
            [0] => pear
            [COLOUR] => green
            [1] => green
        )

    [1] => Array
        (
            [NAME] => watermelon
            [0] => watermelon
            [COLOUR] => pink
            [1] => pink
        )

)

Example #2 获取结果集中单独一列的所有值

下面例子演示了如何从一个结果集中返回单独一列所有的值，尽管 SQL 语句自身可能返回每行多列。

<?php
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();

/* 获取第一列所有值 */
$result = $sth->fetchAll(PDO::FETCH_COLUMN, 0);
var_dump($result);
?>

以上例程的输出类似于：

Array(3)
(
    [0] =>
    string(5) => apple
    [1] =>
    string(4) => pear
    [2] =>
    string(10) => watermelon
)

Example #3 根据单独的一列把所有值分组

下面例子演示了如何返回一个根据结果集中指定列的值分组的关联数组。该数组包含三个键：返回的 apple 和 pear 数组包含了两种不同的颜色，而返回的 watermelon 数组仅包含一种颜色。

<?php
$insert = $dbh->prepare("INSERT INTO fruit(name, colour) VALUES (?, ?)");
$insert->execute(array('apple', 'green'));
$insert->execute(array('pear', 'yellow'));

$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();

/* 根据第一列分组  */
var_dump($sth->fetchAll(PDO::FETCH_COLUMN|PDO::FETCH_GROUP));
?>

以上例程的输出类似于：

array(3) {
  ["apple"]=>
  array(2) {
    [0]=>
    string(5) "green"
    [1]=>
    string(3) "red"
  }
  ["pear"]=>
  array(2) {
    [0]=>
    string(5) "green"
    [1]=>
    string(6) "yellow"
  }
  ["watermelon"]=>
  array(1) {
    [0]=>
    string(5) "green"
  }
}

Example #4 每行结果实例化一个类

下面列子演示了 PDO::FETCH_CLASS 获取风格的行为。

<?php
class fruit {
    public $name;
    public $colour;
}

$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();

$result = $sth->fetchAll(PDO::FETCH_CLASS, "fruit");
var_dump($result);
?>

以上例程的输出类似于：

array(3) {
  [0]=>
  object(fruit)#1 (2) {
    ["name"]=>
    string(5) "apple"
    ["colour"]=>
    string(5) "green"
  }
  [1]=>
  object(fruit)#2 (2) {
    ["name"]=>
    string(4) "pear"
    ["colour"]=>
    string(6) "yellow"
  }
  [2]=>
  object(fruit)#3 (2) {
    ["name"]=>
    string(10) "watermelon"
    ["colour"]=>
    string(4) "pink"
  }
}

Example #5 每行调用一次函数

下面列子演示了 PDO::FETCH_FUNC 获取风格的行为。

<?php
function fruit($name, $colour) {
    return "{$name}: {$colour}";
}

$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();

$result = $sth->fetchAll(PDO::FETCH_FUNC, "fruit");
var_dump($result);
?>

以上例程的输出类似于：

array(3) {
  [0]=>
  string(12) "apple: green"
  [1]=>
  string(12) "pear: yellow"
  [2]=>
  string(16) "watermelon: pink"
}

参见

User Contributed Notes

php at erikthiart dot com 25-Jun-2021 11:21
I am adding this here as I don't seem to find any clear and easy to find examples and explanations of PDO::FETCH_GROUP and how it works by means of an example.

I find this to be one of the most useful modes available in fetchAll() when you need to work with any form of grouping.

In essence, PDO can group results into nested arrays, based on the first field selected.

Example

<?php

$data = $pdo->query('SELECT sex, name, car FROM users')->fetchAll(PDO::FETCH_GROUP);

/* array (
  'male' => array ( 0 =>
    array (
      'name' => 'John',
      'car' => 'Toyota',
    ),
    1 => array (
      'name' => 'Mike',
      'car' => 'Ford',
    ),
  ),
  'female' => array (
    0 => array (
      'name' => 'Mary',
      'car' => 'Mazda',
    ),
    1 => array (
      'name' => 'Kathy',
      'car' => 'Mazda',
    ),
  ),
) */

?>

Tip: If you need to group the data by something other than the first field then you can do it like this as well

<?php
SELECT sex, users.* FROM users
?>
herhor67 at interia dot pl 12-Dec-2020 10:00
I noticed quite a weird (at least for me) behaviour. Maybe it can help someone who will struggle with this too.

<?php
$stmt = new PDOStatement();
$foo  = $stmt->fetchAll();
var_dump($foo);

$stmt = $pdo->prepare('SELECT VERSION()');
$foo  = $stmt->fetchAll();
var_dump($foo);

$stmt = $pdo->prepare("INSERT INTO `tblnm` (date) VALUES (NOW())");
$stmt->execute();
$foo  = $stmt->fetchAll();
var_dump($foo);

$stmt = $pdo->query("INSERT INTO `tblnm` (date) VALUES (NOW())");
$foo  = $stmt->fetchAll();
var_dump($foo);
?>

The first is just an empty object, so $foo === bool(false)
The second one is not executed, so $foo === array(0) {}
The third and fourth throw exception at fetchAll():
"General error: 2014 Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, [...] you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute."

fetchAll() is already used, and changing the above attribute between true and false changes nothing.
This is probably caused by the INSERT not having any return value. We could use RETURNING in the sql, but it's quite new, so may not yet be supported everywhere.

What finally worked for me, was $pdo->exec() and lastInsertId(), because ID is the only column I needed anyway.
<?php
$count = $pdo->exec('INSERT INTO `tblnm` (date) VALUES (NOW())');
$foo = $pdo->lastInsertId();
var_dump($foo);
?>
Then e.g. $foo === string(2) "93"
geompse at gmail dot com 02-Dec-2020 10:28
There is a breaking change upgrading from PHP<7.4 to PHP 8.0. If your class extend PDOStatement, the PHP 8.0 typed prototype is incompatible :
- PHP 7.4 = public PDOStatement::fetchAll ([ int $fetch_style [, mixed $fetch_argument [, array $ctor_args = array() ]]] ) : array
- PHP 8.0 = public PDOStatement::fetchAll ([ int $mode = PDO::FETCH_BOTH[, mixed ...$args] ]) : array

While they are compatible for a human being, PHP is not enjoying it :
- PHP 7.4 = PHP Warning: Declaration of (your class prototype) should be compatible with (PDOStatement's prototype)
- PHP 8.0 = [PhpCompileError] Declaration of (your class prototype) must be comptable with (PDOStatement's prototype)

Because the first one is a warning, it is not fatal, and you might be happy using PHP 8.0's prototype. My personal solution was to stop extending PDOStatement and thus rewrite associated typing declarations and conditions.
Leonardo Costa linux at linuxmanbr dot com dot br 05-Aug-2019 09:08
Method with Return object (PHP 7.2)

class MySql {

public function __construct()
        {
            parent::__construct();
           
            try{

   
               
                $options = array
                (
                    PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES UTF8"
                );
               
                $this->pdo = new PDO('mysql:host=127.0.0.1;dbname=testuser','dbtest', 'xxxxxxx',$options);
                $this->pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
               
            }catch(PDOException $e) {
                print "Error!: " . $e->getMessage() . "<br/>";
                die();
            }
        }
       
        public function selectAll(string $sql)
        {
            $conn = $this->pdo->query($sql);
            return $conn->fetchAll(PDO::FETCH_OBJ);
        }
}
sidi dot khalifa at live dot fr 19-Jun-2019 09:02
Inject the parameters directly into `fetchAll` instead of using `bindValue`

$query  = "
            SELECT
                    a.total_paid_tax_incl AS prize,
                    a.date_add AS date_add
            FROM orders a
            WHERE a.order_id = :seventeen
                   AND a.name = :name";

// connection (Example in Symfony you use class Connection in namespace Doctrine\DBAL\Connection)
$this->connection->fetchAll($query, ['seventeen' => 70, 'name' => 'Sidi'])
rudigerw at hotmail dot com 26-Apr-2018 09:36
I was blown away that you can actually combine PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE | PDO::FETCH_UNIQUE, because both PDO::FETCH_CLASSTYPE and PDO::FETCH_UNIQUE say they will use the first column, but it turns out PDO::FETCH_CLASSTYPE goes first and then PDO::FETCH_UNIQUE will use the next column. This way you can create an associative array of objects, with one of the table columns as key. For example a query such as

 'SELECT Class, Id, t.* FROM subscriptions_tbl t'

might give you this result:

Array
(
    [20481086] => WConsumerSubscription Object
        (
            [Variant] => 2
            [_Expiration:WSubscriptionModel:private] => DateTime Object
                (
                    [date] => 2018-08-08 00:00:00.000000
                    [timezone_type] => 3
                    [timezone] => UTC
                )

            [Notes] =>
            [Id] => 20481086
            [_Deleted:protected] => 0
            [_VersionNo:protected] => 2
            [ContactId] =>
            [ConsumerId] => 2
        )

    [21878324] => WAdminSubscription Object
        (
            [Variant] =>
            [_Expiration:WSubscriptionModel:private] =>
            [Notes] =>
            [Id] => 21878324
            [_Deleted:protected] => 0
            [_VersionNo:protected] => 1
            [ContactId] =>
        )
)
lu_kors 22-Jan-2018 08:45
You might find yourself wanting to use FETCH_GROUP and FETCH_ASSOC at the same time, to get your table's primary key as the array key - use FETCH_UNIQUE also, or you will probably get some unintended behaivor:
<?php
// $stmt is some query like "SELECT rowid, username, comment"

//with unique
$results = $stmt->fetchAll(PDO::FETCH_GROUP|PDO::FETCH_ASSOC|PDO::FETCH_UNIQUE);
$results = array(
    1234 => array('username' => 'abc', 'comment' => '[...]'),
    1235 => array('username' => 'def', 'comment' => '[...]'),
);
//without unique
$results = $stmt->fetchAll(PDO::FETCH_GROUP|PDO::FETCH_ASSOC);
// It does work, but not as you might expect:
$results = array(
    1234 => array(0 => array('username' => 'abc', 'comment' => '[...]')),
    1235 => array(0 => array('username' => 'def', 'comment' => '[...]')),
);
?>
Credit to Ant P. for minimal Example (which i shamelessly copied from the note above me). Thanks a lot!
Anonymous 14-Feb-2017 11:24
Be careful when using PDO::FETCH_COLUMN with PDO::FETCH_GROUP. By default, results are grouped by first column (index 0) and second column (index 1) is returned. But, if you provide fetch argument, it wouldn't affect returned column, but grouping column. If grouping column is set explicitly , first columns is returned instead of second.

<?php
$insert = $dbh->prepare("INSERT INTO people(id, gender) VALUES (?, ?)");
$insert->execute(array('2', 'female'));
$insert->execute(array('3', 'female'));
$insert->execute(array('4', 'female'));
$insert->execute(array('5', 'male'));
$insert->execute(array('6', 'male'));

$sth = $dbh->prepare("SELECT gender, id FROM people");
$sth->execute();

/* Group values by the first column */
var_dump($sth->fetchAll(PDO::FETCH_COLUMN|PDO::FETCH_GROUP));
?>
Returns:
<?php
array (size=2)
  'female' =>
    array (size=3)
      0 => string '2' (length=1)
      1 => string '3' (length=1)
      2 => string '4' (length=1)
  'male' =>
    array (size=2)
      0 => string '5' (length=1)
      1 => string '6' (length=1)
?>

But,
<?php
var_dump($sth->fetchAll(PDO::FETCH_COLUMN|PDO::FETCH_GROUP, 0));
?>
returns:
<?php
array (size=2)
  'female' =>
    array (size=3)
      0 => string 'female' (length=1)
      1 => string 'female' (length=1)
      2 => string 'female' (length=1)
  'male' =>
    array (size=2)
      0 => string 'male' (length=1)
      1 => string 'male' (length=1)
?>
and
<?php
var_dump($sth->fetchAll(PDO::FETCH_COLUMN|PDO::FETCH_GROUP, 1));
?>
returns
<?php
array (size=5)
  2 =>
    array (size=1)
      0 => string 'female' (length=1)
  3 =>
    array (size=1)
      0 => string 'female' (length=1)
  4 =>
    array (size=1)
      0 => string 'female' (length=1)
  5 =>
    array (size=1)
      0 => string 'male' (length=1)
  6 =>
    array (size=1)
      0 => string 'male' (length=1)
?>

First column is retuned and grouping is done by provided column index.
simplerezo at gmail dot com 24-Jan-2017 02:52
I still don't understand why FETCH_KEY_PAIR is not documented here (http://php.net/manual/fr/pdo.constants.php), because it could be very useful!

<?php
  var_dump($pdo->query('select id, name from table')->fetchAll(PDO::FETCH_KEY_PAIR));
?>

This will display:
array(2) {
  [2]=>
  string(10) "name2"
  [5]=>
  string(10) "name5"
}
jeroen dot deklerk at hotmail dot com 16-Nov-2016 11:47
I was having trouble with returning PDO query results in arrays, due to the structure of the results of those queries (query array with arrays for results inside). Now when executing a fetchAll() on a query you get the following:

Array ( [0] = Array ( [key1] => "value1", [key2] => "value2") [1] = Array( [key1] => "value1", [key2] => "value2") )

This is a smaller array, but return results in a HUGE database this way and it quickly becomes IMPPOSIBRU to read out the array given.

This is where the glorious foreach comes in! We all know the basic writing of a foreach (foreach ($array as $key => $value) {...}), but with query results there's a twist, as both the $key AND $value variables are arrays, where $key is the array of the query containing the result arrays and $value is/are the result array(s) themselves.

So in this foreach we have to talk directly to $value to get our results! This would look something like this:

<?php

  foreach ($query as $key => $value) {
      return $value["key2"];
  }

?>

This already does the job, but to return them in arrays we have to change our return code a little bit, like so:

<?php

   foreach ($query as $key => $value) {
      return array (
             "key1" => $value["key1"],
             "key2" => $value["key2"]
      );
   }

?>

This foreach loops through the query array, just like the firs one, but the return code just doesn't return the keys representing the result arrays ($key) and returns only keys from inside the result arrays,  stored in $value. This gives us an array looking like this:

Array ( [key1] => "value1", [key2] => "value2")

This should return all the values in your array, if written properly. I'm still having problems with the foreach not returning ALL results, but this note was mainly to show how it can be returned in an array.
Dean S. 30-Oct-2015 08:38
Using fetchAll() with the fetch types PDO::FETCH_GROUP and PDO::FETCH_ASSOC, PDO::FETCH_CLASS will always use the first column in the selected table as the key for the row in the output...
info at yuriblanc dot it 14-Sep-2015 12:48
Something missing in the doc.
If for instance you try to fetchAll(PDO::CLASS, "Class") it sometimes return an array of objects with NULL values, but the count of objects fetched correspond to table rows.

In this way works fine:
fetchAll(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, "Class");

For example

$stm = $pdo->prepare("SELECT * FROM Fruit");
$stm->execute();
$stm->fetchAll(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, "Fruit");
akira at etnforum dot com 13-Mar-2015 07:41
There may be some user who needs to upgrade their MySQL class to PDO class. The way of fetching results were changed from while loop into a foreach loop. For the people who wish to fetch the results in a while loop, here is a simple trick.

<?php

$db = new DB();
$query = $db->prepare("SELECT * FROM CPUCategory");
$query = $db->execute();
$result = $db->fetchAll();
var_dump($result);

?>

The Output will be:
array(2) {
    [0]=> array(2) {
        ["ccatid"]=> int(1)
        ["ccatname"]=> string(5) "Intel"
    }
    [1]=> array(2) {
        ["ccatid"]=> int(2)
        ["ccatname"]=> string(3) "AMD"
    }
}

Never look like the output of old function.
[ORIGINAL STYLE] mysql_fetch_array($query)
[   MYSQL CLASS] $db->fetch_array($query)

And you may give up.
But there is a simple way to use while loop to fetch the results.

<?php

$db = new DB();
$query = $db->prepare("SELECT * FROM CPUCategory");
$query = $db->execute();
$result = $db->fetchAll();
$row = array_shift($result);
// If you need to fetch them now, put it in a while loop just like below:
// while($row = array_shift($result)) { ... }
   
var_dump($row);

?>

The Output will be in a single array with while loop returns TRUE:
array(2) {
    ["ccatid"]=> int(1)
    ["ccatname"]=> string(5) "Intel"
}

So after fetching this row, while loop runs again and fetch the next row until all row has fetched, then the while loop will return false. (Just like the old function did)

When you need to upgrade to PDO class, not much code needs to be modified and remember.
dyukemedia at gmail dot com 16-Dec-2014 12:15
Getting foreach to play nicely with some data from PDO FetchAll()
I was not understanding to use the $value part of the foreach properly, I hope this helps someone else.
Example:
<?php
$stmt = $this->db->prepare('SELECT title, FMarticle_id FROM articles WHERE domain_name =:domain_name');
            $stmt->bindValue(':domain_name', $domain);
            $stmt->execute();
            $article_list = $stmt->fetchAll(PDO::FETCH_ASSOC);
?>
which gives:

array (size=2)
  0 =>
    array (size=2)
      'title' => string 'About Cats Really Long title for the article' (length=44)
      'FMarticle_id' => string '7CAEBB15-6784-3A41-909A-1B6D12667499' (length=36)
  1 =>
    array (size=2)
      'title' => string 'another cat story' (length=17)
      'FMarticle_id' => string '0BB86A06-2A79-3145-8A02-ECF6EA5C405C' (length=36)

Then use:
<?php
foreach ($article_list as $row => $link) {
  echo  '<a href="'.  $link['FMarticle_id'].'">' . $link['title']. '</a></br>';
  }
?>
janniet at kiekies dot net 27-Oct-2014 02:30
If you want to fetch rows as an object for which you have not defined a class, you can do:
<?php
$result = $q->fetchAll(PDO::FETCH_OBJ);
?>
fractalesque at gmail dot com 09-Jun-2014 04:05
to fetch rows grouped by primary id or any other field you may use FETCH_GROUP with FETCH_UNIQUE:

<?php

//prepare and execute a statement returning multiple rows, on a single one
$stmt = $db->prepare('SELECT id,name,role FROM table');
$stmt->execute();
var_dump($stmt->fetchAll(PDO::FETCH_GROUP | PDO::FETCH_UNIQUE));

//returns an array with the first selected field as key containing associative arrays with the row. This mode takes care not to repeat the key in corresponding grouped array.

$result = array
 (1 => array
   ('name'=>'foo',
    'role'=>'sage',),
  2 => array
   ('name'=>'bar',
    'role'=>'rage',),);

// 'SELECT name,id,role FROM table' would result in that:

$result = array
 ('foo' => array
   ('id'=>1,
    'role'=>'sage',),
  'bar' => array
   ('id'=>2,
    'role'=>'rage',),);

?>
GyoreG 05-Jun-2014 09:14
If you would like to get the result as "key-value-pairs", like:

Array(
    [key1] => "value1"
    [key2] => "value2"
)

then you can do it by calling fetchAll with PDO::FETCH_GROUP | PDO::FETCH_COLUMN parameters.

<?php
  $result = $query->fetchAll(PDO::FETCH_GROUP|PDO::FETCH_COLUMN);
?>
michael dot arnauts at gmail dot com 29-Jan-2014 03:59
If you want to use PDO::FETCH_CLASS but don't like that all the values are of the type string, you can always use the __construct function of the class specified to convert them to a different type.

Another way is using mysqlnd, but it seems I had to recompile PHP for that.

<?php

class Cdr {
    public $a; // int
    public $b; // float
    public $c; // string
   
    public function __construct() {
        $this->a = intval($this->a);
        $this->b = floatval($this->b);
    }
    
}

// ...
$arrCdrs = $objSqlStatement->fetchAll(PDO::FETCH_CLASS, 'Cdr');

?>
ramon at monztro dot com 25-May-2012 04:18
If you are trying to call PDOStatement::fetchAll and is not getting the result set as expected (empty instead), check if you called PDOStatement::execute first.

Remember PDOStatement::fetchAll does not execute the query, it just mounts the array.

:)
Hayley Watson 04-Jul-2011 04:48
If you use the PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE flags to map columns to object properties, fetchAll() will use any __set() method your object has when carrying out the mapping.
Anonymous 25-Jun-2011 02:10
Note that fetchAll() can be extremely memory inefficient for large data sets. My memory limit was set to 160 MB this is what happened when I tried:

<?php
$arr = $stmt->fetchAll();
// Fatal error: Allowed memory size of 16777216 bytes exhausted
?>

If you are going to loop through the output array of fetchAll(), instead use fetch() to minimize memory usage as follows:

<?php
while ($arr = $stmt->fetch()) {
    echo round(memory_get_usage() / (1024*1024),3) .' MB<br />';
    // do_other_stuff();
}
// Last line for the same query shows only 28.973 MB usage
?>
Dennis 10-Jun-2010 08:51
Error:
SQLSTATE[HY000]: General error: 2014 Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute.

If you're using something like:

while ($row = $query->fetchObject()) {
    [...]
}

try using this instead:

$rows = $query->fetchAll(PDO::FETCH_CLASS, 'ArrayObject');

foreach ($rows as $row) {
    [...]
}
esw at pixeloution dot removeme dot com 18-May-2010 09:17
Interestingly enough, when you use fetchAll, the constructor for your object is called AFTER the properties are assigned. For example:

<?php
class person {
    public $name;

    function __construct() {
       $this->name = $this->name . " is my name.";
    }
}

# set up select from a database here with PDO
$obj = $STH->fetchALL(PDO::FETCH_CLASS, 'person');
?>

Will result in ' is my name' being appended to all the name columns. However if you call it slightly differently:

<?php
$obj = $obj = $STH->fetchAll(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, 'person');
?>

Then the constructor will be called before properties are assigned. I can't find this documented anywhere, so I thought it would be nice to add a note here.
mxrgus 23-Oct-2009 04:22
In method body:

return $pstmt->fetchAll() or die("bad");

will not return correct value, but "1" instead.
Daniel Hofmann 05-May-2009 12:21
PLEASE BE AWARE: If you do an OUTER LEFT JOIN and set PDO FetchALL to PDO::FETCH_ASSOC, any primary key you used in the OUTER LEFT JOIN will be set to a blank if there are no records returned in the JOIN.

For example:
<?php
//query the product table and join to the image table and return any images, if we have any, for each product
$sql = "SELECT * FROM product, image
LEFT OUTER JOIN image ON (product.product_id = image.product_id)";

$array = $stmt->fetchAll(PDO::FETCH_ASSOC);

print_r($array);
?>

The resulting array will look something like this:

Array
(
    [0] => Array
        (
            [product_id] =>
            [notes] => "this product..."
            [brand] => "Best Yet"
            ...

The fix is to simply specify your field names in the SELECT clause instead of using the * as a wild card, or, you can also specify the field in addition to the *. The following example returns the product_id field correctly:

<?php
$sql = "SELECT *, product.product_id FROM product, image
LEFT OUTER JOIN image ON (product.product_id = image.product_id)";

$array = $stmt->fetchAll(PDO::FETCH_ASSOC);

print_r($array);
?>

The resulting array will look something like this:

Array
(
    [0] => Array
        (
            [product_id] => 3
            [notes] => "this product..."
            [brand] => "Best Yet"
            ...
Ant P. 03-Feb-2009 06:37
You might find yourself wanting to use FETCH_GROUP and FETCH_ASSOC at the same time, to get your table's primary key as the array key:
<?php
// $stmt is some query like "SELECT rowid, username, comment"
$results = $stmt->fetchAll(PDO::FETCH_GROUP|PDO::FETCH_ASSOC);

// It does work, but not as you might expect:
$results = array(
    1234 => array(0 => array('username' => 'abc', 'comment' => '[...]')),
    1235 => array(0 => array('username' => 'def', 'comment' => '[...]')),
);

// ...but you can at least strip the useless numbered array out easily:
$results = array_map('reset', $results);
?>
davey at php dot net 02-Nov-2008 06:54
When passing PDO::FETCH_CLASS as the first argument, this method will accept the class name as the second option:

<?php
$query = $pdo->prepare($sql);

$result = $query->execute($values);

if ($result && $query->rowCount() > 0) {
    $records = $query->fetchAll(PDO::FETCH_CLASS, 'Some_Class');
    // $record is now an array of Some_Class objects
}
?>

- Davey
mrshelly at hotmail dot com 30-Oct-2008 07:27
PHP fetchAll Data From SQL Server 2005
if field's data type is varchar(nvarchar), only fetch 255 chars. but the "text" data type is ok.

so, notice! to change the 'varchar' or 'nvarchar' (length > 255) to 'text' data type..

hope to help u.

<?php

$user = 'sa';
$pass = 'pass';

$conn = new PDO('mssql:host=127.0.0.1; dbname=tempdb;', $user, $pass);

$mainSQL = "SELECT field_varchar, field_text FROM table1";
$sth = $conn->prepare($mainSQL);
$sth->setFetchMode(PDO::FETCH_ASSOC);
$sth->execute();
$retRows = $sth->fetchAll();
// the field_varchar field only to fetch 255 chars(max)
// the field_text is ok.

var_dump($retRows);

unset($sth); unset($conn);

?>
harlequin2 at gmx dot de 10-Jun-2008 05:01
There is also another fetch mode supported on Oracle and MSSQL:
PDO::FETCH_ASSOC

> fetches only column names and omits the numeric index.

If you would like to return all columns from an sql statement with column keys as table headers, it's as simple as this:

<?php
$dbh = new PDO("DS", "USERNAME", "PASSWORD");
$stmt = $dbh->prepare("SELECT * FROM tablename");
$stmt->execute();
$arrValues = $stmt->fetchAll(PDO::FETCH_ASSOC);
// open the table
print "<table wdith=\"100%\">\n";
print "<tr>\n";
// add the table headers
foreach ($arrValues[0] as $key => $useless){
    print "<th>$key</th>";
}
print "</tr>";
// display data
foreach ($arrValues as $row){
    print "<tr>";
    foreach ($row as $key => $val){
        print "<td>$val</td>";
    }
    print "</tr>\n";
}
// close the table
print "</table>\n";
?>
Anonymous 01-Jan-2008 11:13
If no rows have been returned, fetchAll returns an empty array.
stas at metalinfo dot ru 18-Oct-2006 06:37
Note, that you can use PDO::FETCH_COLUMN|PDO::FETCH_GROUP pair only while selecting two columns, not like DB_common::getAssoc(), when grouping is set to true.