Zend_Db_Table_RowsetIntroduction
When you run a query against a Table class using the find() or
fetchAll() methods, the result is returned in an object of type
Zend_Db_Table_Rowset_Abstract. A Rowset contains a collection of
objects descending from Zend_Db_Table_Row_Abstract. You can
iterate through the Rowset and access individual Row objects, reading or modifying data
in the Rows.
Fetching a RowsetZend_Db_Table_Abstract provides methods
find() and fetchAll(), each of which
returns an object of type Zend_Db_Table_Rowset_Abstract.
Example of fetching a rowsetfetchAll("bug_status = 'NEW'");
]]>Retrieving Rows from a Rowset
The Rowset itself is usually less interesting than the Rows that it contains. This
section illustrates how to get the Rows that comprise the Rowset.
A legitimate query returns zero rows when no rows in the database match the query
conditions. Therefore, a Rowset object might contain zero Row objects. Since
Zend_Db_Table_Rowset_Abstract implements the
Countable interface, you can use count()
to determine the number of Rows in the Rowset.
Counting the Rows in a RowsetfetchAll("bug_status = 'FIXED'");
$rowCount = count($rowset);
if ($rowCount > 0) {
echo "found $rowCount rows";
} else {
echo 'no rows matched the query';
}
]]>Reading a Single Row from a Rowset
The simplest way to access a Row from a Rowset is to use the
current() method. This is particularly appropriate when the
Rowset contains exactly one Row.
fetchAll("bug_id = 1");
$row = $rowset->current();
]]>
If the Rowset contains zero rows, current() returns
PHP's NULL value.
Iterating through a Rowset
Objects descending from Zend_Db_Table_Rowset_Abstract
implement the SeekableIterator interface, which means you can
loop through them using the foreach() construct. Each value
you retrieve this way is a Zend_Db_Table_Row_Abstract object
that corresponds to one record from the table.
fetchAll();
foreach ($rowset as $row) {
// output 'Zend_Db_Table_Row' or similar
echo get_class($row) . "\n";
// read a column in the row
$status = $row->bug_status;
// modify a column in the current row
$row->assigned_to = 'mmouse';
// write the change to the database
$row->save();
}
]]>Seeking to a known position into a RowsetSeekableIterator allows you to seek to a position that you
would like the iterator to jump to. Simply use the seek()
method for that. Pass it an integer representing the number of the Row you would
like your Rowset to point to next, don't forget that it starts with index 0. If the
index is wrong, ie doesn't exist, an exception will be thrown. You should use
count() to check the number of results before seeking to a
position.
fetchAll();
// takes the iterator to the 9th element (zero is one element) :
$rowset->seek(8);
// retrieve it
$row9 = $rowset->current();
// and use it
$row9->assigned_to = 'mmouse';
$row9->save();
]]>getRow() allows you to get a specific row in the Rowset,
knowing its position; don't forget however that positions start with index zero. The
first parameter for getRow() is an integer for the position
asked. The second optional parameter is a boolean; it tells the Rowset iterator if
it must seek to that position in the same time, or not (default is
FALSE). This method returns a
Zend_Db_Table_Row object by default. If the
position requested does not exist, an exception will be thrown. Here is an example:
fetchAll();
// retrieve the 9th element immediately:
$row9 = $rowset->getRow(8);
// and use it:
$row9->assigned_to = 'mmouse';
$row9->save();
]]>
After you have access to an individual Row object, you can manipulate the Row using
methods described in Zend_Db_Table_Row.
Retrieving a Rowset as an Array
You can access all the data in the Rowset as an array using the
toArray() method of the Rowset object. This returns an array
containing one entry per Row. Each entry is an associative array having keys that
correspond to column names and elements that correspond to the respective column values.
Using toArray()fetchAll();
$rowsetArray = $rowset->toArray();
$rowCount = 1;
foreach ($rowsetArray as $rowArray) {
echo "row #$rowCount:\n";
foreach ($rowArray as $column => $value) {
echo "\t$column => $value\n";
}
++$rowCount;
echo "\n";
}
]]>
The array returned from toArray() is not updateable. That is,
you can modify values in the array as you can with any array, but changes to the array
data are not propagated to the database.
Serializing and Unserializing a Rowset
Objects of type Zend_Db_Table_Rowset_Abstract are serializable.
In a similar fashion to serializing an individual Row object, you can serialize a Rowset
and unserialize it later.
Serializing a Rowset
Simply use PHP's serialize() function to
create a string containing a byte-stream representation of the Rowset object
argument.
fetchAll();
// Convert object to serialized form
$serializedRowset = serialize($rowset);
// Now you can write $serializedRowset to a file, etc.
]]>Unserializing a Serialized Rowset
Use PHP's unserialize() function to
restore a string containing a byte-stream representation of an object. The function
returns the original object.
Note that the Rowset object returned is in a disconnected
state. You can iterate through the Rowset and read the Row objects and their
properties, but you cannot change values in the Rows or execute other methods that
require a database connection (for example, queries against related tables).
current();
echo $row->bug_description;
]]>Why do Rowsets unserialize in a disconnected state?
A serialized object is a string that is readable to anyone who possesses it. It
could be a security risk to store parameters such as database account and password
in plain, unencrypted text in the serialized string. You would not want to store
such data to a text file that is not protected, or send it in an email or other
medium that is easily read by potential attackers. The reader of the serialized
object should not be able to use it to gain access to your database without knowing
valid credentials.
You can reactivate a disconnected Rowset using the setTable()
method. The argument to this method is a valid object of type
Zend_Db_Table_Abstract, which you create. Creating a Table object
requires a live connection to the database, so by reassociating the Table with the
Rowset, the Rowset gains access to the database. Subsequently, you can change values in
the Row objects contained in the Rowset and save the changes to the database.
Reactivating a Rowset as Live DatasetTable($bugs);
$row = $rowset->current();
// Now you can make changes to the row and save them
$row->bug_status = 'FIXED';
$row->save();
]]>
Reactivating a Rowset with setTable() also reactivates all the
Row objects contained in that Rowset.
Extending the Rowset class
You can use an alternative concrete class for instances of Rowsets
by extending Zend_Db_Table_Rowset_Abstract. Specify the custom
Rowset class by name either in the $_rowsetClass
protected member of a Table class, or in the array argument of the
constructor of a Table object.
Specifying a custom Rowset class 'MyRowset'));
]]>
Typically, the standard Zend_Db_Rowset concrete class is
sufficient for most usage. However, you might find it useful
to add new logic to a Rowset, specific to a given Table.
For example, a new method could calculate an aggregate
over all the Rows in the Rowset.
Example of Rowset class with a new methodupdated_at > $max_updated_at) {
$latestRow = $row;
}
}
return $latestRow;
}
}
class Bugs extends Zend_Db_Table_Abstract
{
protected $_name = 'bugs';
protected $_rowsetClass = 'MyBugsRowset';
}
]]>