repo_zf1/documentation/manual/en/module_specs/Zend_Db_Table_Rowset.xml

<?xml version="1.0" encoding="UTF-8"?>
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<sect1 id="zend.db.table.rowset">
    <title>Zend_Db_Table_Rowset</title>

    <sect2 id="zend.db.table.rowset.introduction">
        <title>Introduction</title>

        <para>
            When you run a query against a Table class using the <methodname>find()</methodname> or
            <methodname>fetchAll()</methodname> methods, the result is returned in an object of type
            <classname>Zend_Db_Table_Rowset_Abstract</classname>. A Rowset contains a collection of
            objects descending from <classname>Zend_Db_Table_Row_Abstract</classname>. You can
            iterate through the Rowset and access individual Row objects, reading or modifying data
            in the Rows.
        </para>
    </sect2>

    <sect2 id="zend.db.table.rowset.fetch">
        <title>Fetching a Rowset</title>

        <para>
            <classname>Zend_Db_Table_Abstract</classname> provides methods
            <methodname>find()</methodname> and <methodname>fetchAll()</methodname>, each of which
            returns an object of type <classname>Zend_Db_Table_Rowset_Abstract</classname>.
        </para>

        <example id="zend.db.table.rowset.fetch.example">
            <title>Example of fetching a rowset</title>

            <programlisting language="php"><![CDATA[
$bugs   = new Bugs();
$rowset = $bugs->fetchAll("bug_status = 'NEW'");
]]></programlisting>
        </example>
    </sect2>

    <sect2 id="zend.db.table.rowset.rows">
        <title>Retrieving Rows from a Rowset</title>

        <para>
            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.
        </para>

        <para>
            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
            <classname>Zend_Db_Table_Rowset_Abstract</classname> implements the
            <classname>Countable</classname> interface, you can use <methodname>count()</methodname>
            to determine the number of Rows in the Rowset.
        </para>

        <example id="zend.db.table.rowset.rows.counting.example">
            <title>Counting the Rows in a Rowset</title>

            <programlisting language="php"><![CDATA[
$rowset   = $bugs->fetchAll("bug_status = 'FIXED'");

$rowCount = count($rowset);

if ($rowCount > 0) {
    echo "found $rowCount rows";
} else {
    echo 'no rows matched the query';
}
]]></programlisting>
        </example>

        <example id="zend.db.table.rowset.rows.current.example">
            <title>Reading a Single Row from a Rowset</title>

            <para>
                The simplest way to access a Row from a Rowset is to use the
                <methodname>current()</methodname> method. This is particularly appropriate when the
                Rowset contains exactly one Row.
            </para>

            <programlisting language="php"><![CDATA[
$bugs   = new Bugs();
$rowset = $bugs->fetchAll("bug_id = 1");
$row    = $rowset->current();
]]></programlisting>
        </example>

        <para>
            If the Rowset contains zero rows, <methodname>current()</methodname> returns
            <acronym>PHP</acronym>'s <constant>NULL</constant> value.
        </para>

        <example id="zend.db.table.rowset.rows.iterate.example">
            <title>Iterating through a Rowset</title>

            <para>
                Objects descending from <classname>Zend_Db_Table_Rowset_Abstract</classname>
                implement the <classname>SeekableIterator</classname> interface, which means you can
                loop through them using the <methodname>foreach()</methodname> construct. Each value
                you retrieve this way is a <classname>Zend_Db_Table_Row_Abstract</classname> object
                that corresponds to one record from the table.
            </para>

            <programlisting language="php"><![CDATA[
$bugs = new Bugs();

// fetch all records from the table
$rowset = $bugs->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();
}
]]></programlisting>
        </example>

        <example id="zend.db.table.rowset.rows.seek.example">
            <title>Seeking to a known position into a Rowset</title>

            <para>
                <classname>SeekableIterator</classname> allows you to seek to a position that you
                would like the iterator to jump to. Simply use the <methodname>seek()</methodname>
                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
                <methodname>count()</methodname> to check the number of results before seeking to a
                position.
            </para>

            <programlisting language="php"><![CDATA[
$bugs = new Bugs();

// fetch all records from the table
$rowset = $bugs->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();
]]></programlisting>
        </example>

        <para>
            <methodname>getRow()</methodname> 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 <methodname>getRow()</methodname> 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
            <constant>FALSE</constant>). This method returns a
            <classname>Zend_Db_Table_Row</classname> object by default. If the
            position requested does not exist, an exception will be thrown. Here is an example:
        </para>

        <programlisting language="php"><![CDATA[
$bugs = new Bugs();

// fetch all records from the table
$rowset = $bugs->fetchAll();

// retrieve the 9th element immediately:
$row9 = $rowset->getRow(8);

// and use it:
$row9->assigned_to = 'mmouse';
$row9->save();
]]></programlisting>

        <para>
            After you have access to an individual Row object, you can manipulate the Row using
            methods described in <link linkend="zend.db.table.row">Zend_Db_Table_Row</link>.
        </para>
    </sect2>

    <sect2 id="zend.db.table.rowset.to-array">
        <title>Retrieving a Rowset as an Array</title>

        <para>
            You can access all the data in the Rowset as an array using the
            <methodname>toArray()</methodname> 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.
        </para>

        <example id="zend.db.table.rowset.to-array.example">
            <title>Using toArray()</title>

            <programlisting language="php"><![CDATA[
$bugs   = new Bugs();
$rowset = $bugs->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";
}
]]></programlisting>
        </example>

        <para>
            The array returned from <methodname>toArray()</methodname> 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.
        </para>
    </sect2>

    <sect2 id="zend.db.table.rowset.serialize">
        <title>Serializing and Unserializing a Rowset</title>

        <para>
            Objects of type <classname>Zend_Db_Table_Rowset_Abstract</classname> are serializable.
            In a similar fashion to serializing an individual Row object, you can serialize a Rowset
            and unserialize it later.
        </para>

        <example id="zend.db.table.rowset.serialize.example.serialize">
            <title>Serializing a Rowset</title>

            <para>
                Simply use <acronym>PHP</acronym>'s <methodname>serialize()</methodname> function to
                create a string containing a byte-stream representation of the Rowset object
                argument.
            </para>

            <programlisting language="php"><![CDATA[
$bugs   = new Bugs();
$rowset = $bugs->fetchAll();

// Convert object to serialized form
$serializedRowset = serialize($rowset);

// Now you can write $serializedRowset to a file, etc.
]]></programlisting>
        </example>

        <example id="zend.db.table.rowset.serialize.example.unserialize">
            <title>Unserializing a Serialized Rowset</title>

            <para>
                Use <acronym>PHP</acronym>'s <methodname>unserialize()</methodname> function to
                restore a string containing a byte-stream representation of an object. The function
                returns the original object.
            </para>

            <para>
                Note that the Rowset object returned is in a <emphasis>disconnected</emphasis>
                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).
            </para>

            <programlisting language="php"><![CDATA[
$rowsetDisconnected = unserialize($serializedRowset);

// Now you can use object methods and properties, but read-only
$row = $rowsetDisconnected->current();
echo $row->bug_description;
]]></programlisting>
        </example>

        <note>
            <title>Why do Rowsets unserialize in a disconnected state?</title>

            <para>
                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.
            </para>
        </note>

        <para>
            You can reactivate a disconnected Rowset using the <methodname>setTable()</methodname>
            method. The argument to this method is a valid object of type
            <classname>Zend_Db_Table_Abstract</classname>, 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.
        </para>

        <example id="zend.db.table.rowset.serialize.example.set-table">
            <title>Reactivating a Rowset as Live Data</title>

            <programlisting language="php"><![CDATA[
$rowset = unserialize($serializedRowset);

$bugs = new Bugs();

// Reconnect the rowset to a table, and
// thus to a live database connection
$rowset->setTable($bugs);

$row = $rowset->current();

// Now you can make changes to the row and save them
$row->bug_status = 'FIXED';
$row->save();
]]></programlisting>
        </example>

        <para>
            Reactivating a Rowset with <methodname>setTable()</methodname> also reactivates all the
            Row objects contained in that Rowset.
        </para>
    </sect2>

    <sect2 id="zend.db.table.rowset.extending">
        <title>Extending the Rowset class</title>

        <para>
            You can use an alternative concrete class for instances of Rowsets
            by extending <classname>Zend_Db_Table_Rowset_Abstract</classname>. Specify the custom
            Rowset class by name either in the <varname>$_rowsetClass</varname>
            protected member of a Table class, or in the array argument of the
            constructor of a Table object.
        </para>

        <example id="zend.db.table.rowset.extending.example">
            <title>Specifying a custom Rowset class</title>

            <programlisting language="php"><![CDATA[
class MyRowset extends Zend_Db_Table_Rowset_Abstract
{
    // ...customizations
}

// Specify a custom Rowset to be used by default
// in all instances of a Table class.
class Products extends Zend_Db_Table_Abstract
{
    protected $_name = 'products';
    protected $_rowsetClass = 'MyRowset';
}

// Or specify a custom Rowset to be used in one
// instance of a Table class.
$bugs = new Bugs(array('rowsetClass' => 'MyRowset'));
]]></programlisting>
        </example>

        <para>
            Typically, the standard <classname>Zend_Db_Rowset</classname> 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.
        </para>

        <example id="zend.db.table.rowset.extending.example-aggregate">
            <title>Example of Rowset class with a new method</title>

            <programlisting language="php"><![CDATA[
class MyBugsRowset extends Zend_Db_Table_Rowset_Abstract
{
    /**
     * Find the Row in the current Rowset with the
     * greatest value in its 'updated_at' column.
     */
    public function getLatestUpdatedRow()
    {
        $max_updated_at = 0;
        $latestRow = null;
        foreach ($this as $row) {
            if ($row->updated_at > $max_updated_at) {
                $latestRow = $row;
            }
        }
        return $latestRow;
    }
}

class Bugs extends Zend_Db_Table_Abstract
{
    protected $_name = 'bugs';
    protected $_rowsetClass = 'MyBugsRowset';
}
]]></programlisting>
        </example>
    </sect2>
</sect1>
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