repo_zf1/documentation/manual/en/module_specs/Zend_Controller-Response.xml

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<sect1 id="zend.controller.response">
    <title>The Response Object</title>

    <sect2 id="zend.controller.response.usage">
        <title>Usage</title>

        <para>
            The response object is the logical counterpart to the <link
                linkend="zend.controller.request">request object</link>. Its
            purpose is to collate content and/or headers so that they may be
            returned en masse. Additionally, the front controller will pass any
            caught exceptions to the response object, allowing the developer to
            gracefully handle exceptions. This functionality may be overridden
            by setting
            <methodname>Zend_Controller_Front::throwExceptions(true)</methodname>:
        </para>

        <programlisting language="php"><![CDATA[
$front->throwExceptions(true);
]]></programlisting>

        <para>
            To send the response output, including headers, use
            <methodname>sendResponse()</methodname>.
        </para>

        <programlisting language="php"><![CDATA[
$response->sendResponse();
]]></programlisting>

        <note>
            <para>
                By default, the front controller calls <methodname>sendResponse()</methodname>
                when it has finished dispatching the request; typically you will
                never need to call it. However, if you wish to manipulate the
                response or use it in testing, you can override this
                behaviour by setting the <property>returnResponse</property> flag with
                <methodname>Zend_Controller_Front::returnResponse(true)</methodname>:
            </para>

            <programlisting language="php"><![CDATA[
$front->returnResponse(true);
$response = $front->dispatch();

// do some more processing, such as logging...
// and then send the output:
$response->sendResponse();
]]></programlisting>
        </note>

        <para>
            Developers should make use of the response object in their action
            controllers. Instead of directly rendering output and sending
            headers, push them to the response object:
        </para>

        <programlisting language="php"><![CDATA[
// Within an action controller action:
// Set a header
$this->getResponse()
    ->setHeader('Content-Type', 'text/html')
    ->appendBody($content);
]]></programlisting>

        <para>
            By doing this, all headers get sent at once, just prior to
            displaying the content.
        </para>

        <note>
            <para>
                If using the action controller <link
                    linkend="zend.controller.action.viewintegration">view
                    integration</link>, you do not need to set the rendered view
                script content in the response object, as
                <methodname>Zend_Controller_Action::render()</methodname> does this by default.
            </para>
        </note>

        <para>
            Should an exception occur in an application, check the response object's
            <methodname>isException()</methodname> flag, and retrieve the exception using
            <methodname>getException()</methodname>. Additionally, one may create custom
            response objects that redirect to error pages, log exception messages,
            do pretty formatting of exception messages (for development
            environments), etc.
        </para>

        <para>
            You may retrieve the response object following the front controller
            <methodname>dispatch()</methodname>, or request the front controller to return the
            response object instead of rendering output.
        </para>

        <programlisting language="php"><![CDATA[
// retrieve post-dispatch:
$front->dispatch();
$response = $front->getResponse();
if ($response->isException()) {
    // log, mail, etc...
}

// Or, have the front controller dispatch() process return it
$front->returnResponse(true);
$response = $front->dispatch();

// do some processing...

// finally, echo the response
$response->sendResponse();
]]></programlisting>

        <para>
            By default, exception messages are not displayed. This behaviour may be
            overridden by calling <methodname>renderExceptions()</methodname>, or enabling the
            front controller to <methodname>throwExceptions()</methodname>, as shown above:
        </para>

        <programlisting language="php"><![CDATA[
$response->renderExceptions(true);
$front->dispatch($request, $response);

// or:
$front->returnResponse(true);
$response = $front->dispatch();
$response->renderExceptions();
$response->sendResponse();

// or:
$front->throwExceptions(true);
$front->dispatch();
]]></programlisting>
    </sect2>

    <sect2 id="zend.controller.response.headers">
        <title>Manipulating Headers</title>

        <para>
            As stated previously, one aspect of the response object's duties is
            to collect and emit <acronym>HTTP</acronym> response headers. A variety of methods
            exist for this:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <methodname>canSendHeaders()</methodname> is used to determine if
                    headers have already been sent. It takes an optional flag
                    indicating whether or not to throw an exception if headers
                    have already been sent. This can be overridden by setting
                    the property <property>headersSentThrowsException</property> to
                    <constant>FALSE</constant>.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>setHeader($name, $value, $replace = false)</methodname> is
                    used to set an individual header. By default, it does not
                    replace existing headers of the same name in the object;
                    however, setting <varname>$replace</varname> to <constant>TRUE</constant> will
                    force it to do so.
                </para>

                <para>
                    Before setting the header, it checks with
                    <methodname>canSendHeaders()</methodname> to see if this operation is
                    allowed at this point, and requests that an exception be
                    thrown.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>setRedirect($url, $code = 302)</methodname> sets an
                    <acronym>HTTP</acronym> Location header for a redirect. If an
                    <acronym>HTTP</acronym> status code has been provided, it will use that status
                    code.
                </para>

                <para>
                    Internally, it calls <methodname>setHeader()</methodname> with the
                    <varname>$replace</varname> flag on to ensure only one such header
                    is ever sent.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getHeaders()</methodname> returns an array of all headers.
                    Each array element is an array with the keys 'name' and
                    'value'.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>clearHeaders()</methodname> clears all registered headers.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>setRawHeader()</methodname> can be used to set headers that
                    are not key and value pairs, such as an <acronym>HTTP</acronym> status header.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getRawHeaders()</methodname> returns any registered raw
                    headers.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>clearRawHeaders()</methodname> clears any registered raw
                    headers.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>clearAllHeaders()</methodname> clears both regular key and value
                    headers as well as raw headers.
                </para>
            </listitem>
        </itemizedlist>

        <para>
            In addition to the above methods, there are accessors for setting
            and retrieving the <acronym>HTTP</acronym> response code for the current request,
            <methodname>setHttpResponseCode()</methodname> and
            <methodname>getHttpResponseCode()</methodname>.
        </para>
    </sect2>

    <sect2 id="zend.controller.response.namedsegments">
        <title>Named Segments</title>

        <para>
            The response object has support for "named segments". This allows
            you to segregate body content into different segments and order
            those segments so output is returned in a specific order.
            Internally, body content is saved as an array, and the various
            accessor methods can be used to indicate placement and names within
            that array.
        </para>

        <para>
            As an example, you could use a <methodname>preDispatch()</methodname> hook to
            add a header to the response object, then have the action controller
            add body content, and a <methodname>postDispatch()</methodname> hook add a
            footer:
        </para>

        <programlisting language="php"><![CDATA[
// Assume that this plugin class is registered with the front controller
class MyPlugin extends Zend_Controller_Plugin_Abstract
{
    public function preDispatch(Zend_Controller_Request_Abstract $request)
    {
        $response = $this->getResponse();
        $view = new Zend_View();
        $view->setBasePath('../views/scripts');

        $response->prepend('header', $view->render('header.phtml'));
    }

    public function postDispatch(Zend_Controller_Request_Abstract $request)
    {
        $response = $this->getResponse();
        $view = new Zend_View();
        $view->setBasePath('../views/scripts');

        $response->append('footer', $view->render('footer.phtml'));
    }
}

// a sample action controller
class MyController extends Zend_Controller_Action
{
    public function fooAction()
    {
        $this->render();
    }
}
]]></programlisting>

        <para>
            In the above example, a call to <filename>/my/foo</filename> will cause the
            final body content of the response object to have the following
            structure:
        </para>

        <programlisting language="php"><![CDATA[
array(
    'header'  => ..., // header content
    'default' => ..., // body content from MyController::fooAction()
    'footer'  => ...  // footer content
);
]]></programlisting>

        <para>
            When this is rendered, it will render in the order in which elements
            are arranged in the array.
        </para>

        <para>
            A variety of methods can be used to manipulate the named segments:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <methodname>setBody()</methodname> and <methodname>appendBody()</methodname>
                    both allow you to pass a second value, <varname>$name</varname>,
                    indicating a named segment. In each case, if you provide
                    this, it will overwrite that specific named segment or
                    create it if it does not exist (appending to the array by
                    default). If no named segment is passed to
                    <methodname>setBody()</methodname>, it resets the entire body content
                    array. If no named segment is passed to <methodname>appendBody()</methodname>,
                    the content is appended to the value in the 'default' name
                    segment.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>prepend($name, $content)</methodname> will create a segment
                    named <varname>$name</varname> and place it at the beginning of
                    the array. If the segment exists already, it will be removed
                    prior to the operation (i.e., overwritten and replaced).
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>append($name, $content)</methodname> will create a segment
                    named <varname>$name</varname> and place it at the end of
                    the array. If the segment exists already, it will be removed
                    prior to the operation (i.e., overwritten and replaced).
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>insert($name, $content, $parent = null, $before =
                        false)</methodname> will create a segment named
                    <varname>$name</varname>. If provided with a <varname>$parent</varname>
                    segment, the new segment will be placed either before or
                    after that segment (based on the value of
                    <varname>$before</varname>) in the array. If the segment exists
                    already, it will be removed prior to the operation (i.e.,
                    overwritten and replaced).
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>clearBody($name = null)</methodname> will remove a single
                    named segment if a <varname>$name</varname> is provided (and the
                    entire array otherwise).
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getBody($spec = false)</methodname> can be used to retrieve a
                    single array segment if <varname>$spec</varname> is the name of a named
                    segment. If <varname>$spec</varname> is <constant>FALSE</constant>, it returns
                    a string formed by concatenating all named segments in order. If
                    <varname>$spec</varname> is <constant>TRUE</constant>, it returns the body
                    content array.
                </para>
            </listitem>
        </itemizedlist>
    </sect2>

    <sect2 id="zend.controller.response.exceptions">
        <title>Testing for Exceptions in the Response Object</title>

        <para>
            As mentioned earlier, by default, exceptions caught during dispatch
            are registered with the response object. Exceptions are registered
            in a stack, which allows you to keep all exceptions thrown --
            application exceptions, dispatch exceptions, plugin exceptions, etc.
            Should you wish to check for particular exceptions or to log
            exceptions, you'll want to use the response object's exception <acronym>API</acronym>:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <methodname>setException(Exception $e)</methodname> allows you to
                    register an exception.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>isException()</methodname> will tell you if an exception has
                    been registered.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getException()</methodname> returns the entire
                    exception stack.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>hasExceptionOfType($type)</methodname> allows you to
                    determine if an exception of a particular class is in the
                    stack.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>hasExceptionOfMessage($message)</methodname> allows you to
                    determine if an exception with a specific message is in the
                    stack.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>hasExceptionOfCode($code)</methodname> allows you to
                    determine if an exception with a specific code is in the
                    stack.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getExceptionByType($type)</methodname> allows you to
                    retrieve all exceptions of a specific class from the stack.
                    It will return <constant>FALSE</constant> if none are found, and an array of
                    exceptions otherwise.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getExceptionByMessage($message)</methodname> allows you to
                    retrieve all exceptions with a specific message from the stack.
                    It will return <constant>FALSE</constant> if none are found, and an array of
                    exceptions otherwise.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>getExceptionByCode($code)</methodname> allows you to
                    retrieve all exceptions with a specific code from the stack.
                    It will return <constant>FALSE</constant> if none are found, and an array of
                    exceptions otherwise.
                </para>
            </listitem>

            <listitem>
                <para>
                    <methodname>renderExceptions($flag)</methodname> allows you to set a
                    flag indicating whether or not exceptions should be emitted
                    when the response is sent.
                </para>
            </listitem>
        </itemizedlist>
    </sect2>

    <sect2 id="zend.controller.response.subclassing">
        <title>Subclassing the Response Object</title>

        <para>
            The purpose of the response object is to collect headers and content
            from the various actions and plugins and return them to the client;
            secondarily, it also collects any errors (exceptions) that occur in
            order to process them, return them, or hide them from the end user.
        </para>

        <para>
            The base response class is
            <classname>Zend_Controller_Response_Abstract</classname>, and any subclass you
            create should extend that class or one of its derivatives. The
            various methods available have been listed in the previous sections.
        </para>

        <para>
            Reasons to subclass the response object include modifying how output
            is returned based on the request environment (e.g., not sending
            headers for <acronym>CLI</acronym> or <acronym>PHP</acronym>-<acronym>GTK</acronym>
            requests), adding functionality to return a final view based on content stored in named
            segments, etc.
        </para>
    </sect2>
</sect1>
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