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(PHP 5 >= 5.1.0, PECL pdo >= 0.1.0)
PDOStatement->fetch — Fetches the next row from a result set
Fetches a row from a result set associated with a PDOStatement object. The fetch_style parameter determines how PDO returns the row.
Controls how the next row will be returned to the caller. This value must be one of the PDO::FETCH_* constants, defaulting to PDO::FETCH_BOTH.
PDO::FETCH_ASSOC: returns an array indexed by column name as returned in your result set
PDO::FETCH_BOTH (default): returns an array indexed by both column name and 0-indexed column number as returned in your result set
PDO::FETCH_BOUND: returns TRUE and assigns the values of the columns in your result set to the PHP variables to which they were bound with the PDOStatement::bindColumn() method
PDO::FETCH_CLASS: returns a new instance of the requested class, mapping the columns of the result set to named properties in the class. If fetch_style includes PDO::FETCH_CLASSTYPE (e.g. PDO::FETCH_CLASS | PDO::FETCH_CLASSTYPE) then the name of the class is determined from a value of the first column.
PDO::FETCH_INTO: updates an existing instance of the requested class, mapping the columns of the result set to named properties in the class
PDO::FETCH_LAZY: combines PDO::FETCH_BOTH and PDO::FETCH_OBJ, creating the object variable names as they are accessed
PDO::FETCH_NUM: returns an array indexed by column number as returned in your result set, starting at column 0
PDO::FETCH_OBJ: returns an anonymous object with property names that correspond to the column names returned in your result set
For a PDOStatement object representing a scrollable cursor, this value determines which row will be returned to the caller. This value must be one of the PDO::FETCH_ORI_* constants, defaulting to PDO::FETCH_ORI_NEXT. To request a scrollable cursor for your PDOStatement object, you must set the PDO::ATTR_CURSOR attribute to PDO::CURSOR_SCROLL when you prepare the SQL statement with PDO::prepare().
For a PDOStatement object representing a scrollable cursor for which the cursor_orientation parameter is set to PDO::FETCH_ORI_ABS, this value specifies the absolute number of the row in the result set that shall be fetched.
For a PDOStatement object representing a scrollable cursor for which the cursor_orientation parameter is set to PDO::FETCH_ORI_REL, this value specifies the row to fetch relative to the cursor position before PDOStatement::fetch() was called.
The return value of this function on success depends on the fetch type. In all cases, FALSE is returned on failure.
Beispiel #1 Fetching rows using different fetch styles
<?php
$sth = $dbh->prepare("SELECT name, colour FROM fruit");
$sth->execute();
/* Exercise PDOStatement::fetch styles */
print("PDO::FETCH_ASSOC: ");
print("Return next row as an array indexed by column name\n");
$result = $sth->fetch(PDO::FETCH_ASSOC);
print_r($result);
print("\n");
print("PDO::FETCH_BOTH: ");
print("Return next row as an array indexed by both column name and number\n");
$result = $sth->fetch(PDO::FETCH_BOTH);
print_r($result);
print("\n");
print("PDO::FETCH_LAZY: ");
print("Return next row as an anonymous object with column names as properties\n");
$result = $sth->fetch(PDO::FETCH_LAZY);
print_r($result);
print("\n");
print("PDO::FETCH_OBJ: ");
print("Return next row as an anonymous object with column names as properties\n");
$result = $sth->fetch(PDO::FETCH_OBJ);
print $result->NAME;
print("\n");
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
PDO::FETCH_ASSOC: Return next row as an array indexed by column name
Array
(
[NAME] => apple
[COLOUR] => red
)
PDO::FETCH_BOTH: Return next row as an array indexed by both column name and number
Array
(
[NAME] => banana
[0] => banana
[COLOUR] => yellow
[1] => yellow
)
PDO::FETCH_LAZY: Return next row as an anonymous object with column names as properties
PDORow Object
(
[NAME] => orange
[COLOUR] => orange
)
PDO::FETCH_OBJ: Return next row as an anonymous object with column names as properties
kiwi
Beispiel #2 Fetching rows with a scrollable cursor
<?php
function readDataForwards($dbh) {
$sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY BET';
try {
$stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
$stmt->execute();
while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT)) {
$data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\n";
print $data;
}
$stmt = null;
}
catch (PDOException $e) {
print $e->getMessage();
}
}
function readDataBackwards($dbh) {
$sql = 'SELECT hand, won, bet FROM mynumbers ORDER BY bet';
try {
$stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
$stmt->execute();
$row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_LAST);
do {
$data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "\n";
print $data;
} while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));
$stmt = null;
}
catch (PDOException $e) {
print $e->getMessage();
}
}
print "Reading forwards:\n";
readDataForwards($conn);
print "Reading backwards:\n";
readDataBackwards($conn);
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
Reading forwards: 21 10 5 16 0 5 19 20 10 Reading backwards: 19 20 10 16 0 5 21 10 5
When fetching an object, the constructor of the class is called after the fields are populated by default.
PDO::FETCH_PROPS_LATE is used to change the behaviour and make it work as expected - constructor be called _before_ the object fields will be populated with the data.
sample:
<?php
$a = $PDO->query('select id from table');
$a->setFetchMode(PDO::FETCH_CLASS|PDO::FETCH_PROPS_LATE, 'ClassName');
$obj = $a->fetch();
?>
http://bugs.php.net/bug.php?id=53394
When fetching multiple rows into an object. It is necessary to clone the objects returned by the PDOStatement::fetch() operation. Otherwise you will just get a list of pointers to the object located inside the statement, containing the information of the last row.
Example:
<?php
$stmt = $pdoLink->prepare("SELECT * FROM `table`;");
$stmt->setFetchMode(PDO::FETCH_INTO, new myClass());
$stmt->execute();
// Assuming there are multiple rows in the table.
while ($object = $stmt->fetch()) {
$result[] = clone $object;
}
var_dump($result);
?>
Here is quick note for developers that use the PDO SQLite Driver:
The PDO SQLite driver does not support cursors, so using the PDO::CURSOR_SCROLL Attribute, will not work when using the PDO SQLite driver. For example:
<?php
// Assuming $Handle Is a PDO Handle.
$Statement = $Handle->query( $sqlStatement , array( PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL ) );
?>
What is even worse is that PDO::prepare will NOT throw an Exception when it fails to prepare the query, even when the error mode is set to throw Exceptions, and will instead return a Boolean False!
Not only do I consider this a poor design choice, but also its a real shame that this is not documented anywhere in the manual -- in fact the manual is not clear on what Attributes are supported by which drivers and which are not so developers are left to play a classic game of guess.
I hope this saves some developers some headaches.
Good Luck,
Just thought I would point out something interesting that caught my eye.
Once you retrieve a PDOStatement, whether for a prepared statement or a normal result set, the connection status of your PDO handle is no longer taken into consideration!
The PHP Manual clearly states that to open a PDO connection, create a new Instance of the PDO Class. To close a PDO connection, destroy the Instance, possibly by setting it to a Null Reference. The PDO Instance in this case is your handle.
Here is the interesting part. If you close the PDO connection, as described above, you can still continue to either execute a prepared statement or iterate through a result set!
For example, the following code will work perfectly fine:
<?php
// Open Handle.
$Handle = new PDO( 'mysql:host=localhost; dbname=LOG' , 'root' );
$Handle->setAttribute( PDO::ATTR_ERRMODE , PDO::ERRMODE_EXCEPTION );
// Prepare Statement.
$Statement = $Handle->prepare( "SELECT * FROM ERROR" );
// Close Handle.
$Handle = null;
// Execute Statement. Amazing How There Is No Problem Even Though The Connection Is Closed!
$Statement->execute();
// Iterate Result. Again, Amazing How There Is No Problem!
while( $row = $Statement->fetch( PDO::FETCH_BOTH , PDO::FETCH_ORI_NEXT ) ) {
}
?>
You do not even need to prepare a statement. A native query also has no problems, like the following code:
<?php
// Open Handle.
$Handle = new PDO( 'mysql:host=localhost; dbname=LOG' , 'root' );
$Handle->setAttribute( PDO::ATTR_ERRMODE , PDO::ERRMODE_EXCEPTION );
// Query Statement.
$Statement = $Handle->query( "SELECT * FROM ERROR" );
// Close Handle.
$Handle = null;
// Iterate Result.
$Statement->fetchAll( );
?>
I am not sure if this is a bug or not but its a big gottcha for developers coming from other envrionments, such as .NET or even those PHP developers used to using the native database functions before PDO came around.
For example, using the native mysql_* Functions, the following will not work:
<?php
mysql_connect( "localhost" , "root");
mysql_select_db( "LOG" );
mysql_close( );
mysql_query( "SELECT * FROM ERROR" );
?>
Good Luck,
A word of caution regarding fh at ez dot no's note: as of PHP 5.2.12 the constructor is called *before* the data is set in FETCH_CLASS mode. The previous behaviour seems to be considered a bug (http://bugs.php.net/bug.php?id=49521), so don't rely on it.
A quick one liner to get the first entry returned. This is nice for very basic queries.
<?php
$count = current($db->query("select count(*) from table")->fetch());
?>php
I spent some hours trying to find out how to manipulate with BLOB fields using PDO.
Remember that you can't retreive BLOB data using something like this :
<?php
$sql = 'SELECT * FROM sometable LIMIT 1';
$stmt = $dbh->prepare($sql);
$stmt->execute();
$stmt->setAttribute(PDO::FETCH_ASSOC);
$row = $stmt->fetch();
$myFile = $row['file'];
?>
Instead of this you should try following approach:
<?php
$sql = "SELECT mime, file FROM sometable LIMIT 1";
$stmt = $dbh->prepare($sql);
$stmt->execute();
$stmt->bindColumn(1, $mime,);
$stmt->bindColumn(2, $file, PDO::PARAM_LOB);
$stmt->fetch();
header('Content-type: '.$mime);
print $file;
?>
Note that PDO::ATTR_STRINGIFY_FETCHES will NOT work for the MySQL driver. MySQL will always return strings because that is the behaviour of the core mysql PHP extension. See http://bugs.php.net/bug.php?id=44341
As an alternative to marcini's suggestion:
You can use:
$dbh->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
...on your PDO connection object to allow query buffering in MySQL. This will eliminate the problem of re-preparing an unclosed statement object.
If you to use a new instance of a class for a record you can use:
<?php
include_once("user.class");
$sth = $db->prepare("SELECT * FROM user WHERE id = 1");
/* create instance automatically */
$sth->setFetchMode( PDO::FETCH_CLASS, 'user');
$sth->execute();
$user = $sth->fetch( PDO::FETCH_CLASS );
$sth->closeCursor();
print ($user->id);
/* or create an instance yourself and use it */
$user= new user();
$sth->setFetchMode( PDO::FETCH_INTO, $user);
$sth->execute();
$user= $sth->fetch( PDO::FETCH_INTO );
$sth->closeCursor();
print ($user->id);
?>
When you do a SELECT query for one row, and want to check if it's there, you don't need to count the fetchAll() result, you can just check if $result->fetch() is true:
<?php
$bbnq = sprintf("SELECT login
FROM users
WHERE id = %u",27);
try
{ $req = $db_bbn->query($bbnq); }
catch (Exception $e)
{ bbnf_pdo_error($e,__FILE__,__LINE__); }
if ( $r = $req->fetch() )
{ echo "This query has a row result"; }
else
{ echo "This query has an empty result"; }
?>
Oops...
The constants are no longer PDO_FETCH_*
They are now class contants PDO::FETCH_*
The documentation above need to be changed appropriately.
>> note that fetch constants are not included in the PDO class for PHP versions prior to 5.1
They appear to not exist in 5.2.3 either, as I am getting the following error:
Notice: Use of undefined constant PDO_FETCH_ASSOC - assumed 'PDO_FETCH_ASSOC' in C:\Documents and Settings\driddle.AUTISMSPEAKS.000\My Documents\ascentral\sqlite_test.php on line 36
Warning: PDOStatement::fetchAll() expects parameter 1 to be long, string given in C:\Documents and Settings\driddle.AUTISMSPEAKS.000\My Documents\ascentral\sqlite_test.php on line 36'
Code to reproduce:
// retrieve and output info from db
$sqlGetEvent = 'SELECT * from calendarItem';
$result = $dbHandle->query($sqlGetEvent);
$data = $result->fetchAll(PDO_FETCH_ASSOC);
Regarding the two previous notes - I downloaded the "latest CVS" a week ago for Windows and was surprised to notice that this issue is gone there, ie you don't have to close cursor before doing next query.
as an alternative for marcini's note:
just clear the statement variable before you issue another query:
<?php
$stmt = $db->prepare('SELECT * FROM test');
// fetch only the first row
$row = $stmt->fetch(PDO::FETCH_ASSOC);
// clear the variable so its contents are destroyed (including the other rows in the result)
$stmt = null;
// now you can issue another query
$stmt = $db->prepare('SELECT * FROM test2');
?>
Be careful with fetch() when you use prepared statements and MySQL (I don`t know how it is with other databases). Fetch won`t close cursor and won`t let you send any other query, even if your result set has only one row, .
If you use $statement->fetch(), you will also have to use $statement->closeCursor() afterwards, to be albe to execute another query.
Alternatively you can use $statement->fetchAll() without $statement->closeCursor().
WARNING:
fetch() does NOT adhere to SQL-92 SQLSTATE standard when dealing with empty datasets.
Instead of setting the errorcode class to 20 to indicate "no data found", it returns a class of 00 indicating success, and returns NULL to the caller.
This also prevents the exception mechainsm from firing.
Programmers will need to explicitly code tests for empty resultsets after any fetch*() instead of relying on the default behavior of the RDBMS.
I tried logging this as a bug, but it was dismissed as "working as intended". Just a head's up.
Note that using the FETCH_CLASS mechanism does NOT trigger the class's constructor! You must explicity instantiate the class to use it's constructor behavior.
I can also add that the constructor is run _after_ the data is set on the object if yo use PDO::FETCH_CLASS.
If you want to use PDO::FETCH_CLASS you need to set it up with setFetchMode first like so:
$stmt->setFetchMode( PDO::FETCH_CLASS, 'classType', array( 'parameters to constructor' );
$object = $stmt->fetch( PDO::FETCH_CLASS );
If you ommit this PHP will segfault.
note that fetch constants are not included in the PDO class for PHP versions prior to 5.1
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