ob_end_clean - PHP code example

The php Function Ob_End_Clean

The php function ob_end_clean removes the contents of an output buffer in php. This allows developers to create optimized web pages as it can prevent unnecessary output from occurring on the page.

By default, echo and other similar functions in php are sent immediately to the browser without any buffering. To improve performance and make things work more efficiently it is advisable to use PHP’s built in output buffering functions that gather the results of echo and other commands into a buffer and send them later, or discard them altogether.

Output buffering is activated by calling ob_start() with PHP_OUTPUT_HANDLER_FLUSHABLE and PHP_OUTPUT_HANDLER_REMOVABLE flags. Once active it can be removed by calling ob_end_flush() or ob_end_clean(). Both functions perform the same task but the difference is that ob_end_flush() also sends the buffer contents to the browser while ob_end_clean() saves the buffer contents in a variable before emptying it.

Buffering is a very useful feature that helps reduce the time it takes for a page to be generated by a server as the HTML can be processed in the background while other components of a webpage are fetching from the browser. However it is important to know when and how to stop the buffering as it may cause problems with dynamically generated content or images in a web page.

By setting a directive in a configuration file that affects all PHP scripts it is possible to disable PHP’s output buffering, but enabling it on a need basis may be preferable. Using PHP’s built in functions like ob_get_contents(), ob_end_flush() and ob_end_clean() is the best way to do this.

ob_end_clean example

    protected function is_filesystem_available() {
        $filesystem_method = get_filesystem_method();

        if ( 'direct' === $filesystem_method ) {
            return true;
        }

        ob_start();
        $filesystem_credentials_are_stored = request_filesystem_credentials( self_admin_url() );
        ob_end_clean();

        if ( $filesystem_credentials_are_stored ) {
            return true;
        }

        return new WP_Error( 'fs_unavailable', __( 'The filesystem is currently unavailable for managing plugins.' ), array( 'status' => 500 ) );
    }

    /** * Retrieves the plugin's schema, conforming to JSON Schema. * * @since 5.5.0 * * @return array Item schema data. */

    public static function closeOutputBuffers(int $targetLevel, bool $flush): void
    {
        $status = ob_get_status(true);
        $level = \count($status);
        $flags = \PHP_OUTPUT_HANDLER_REMOVABLE | ($flush ? \PHP_OUTPUT_HANDLER_FLUSHABLE : \PHP_OUTPUT_HANDLER_CLEANABLE);

        while ($level-- > $targetLevel && ($s = $status[$level]) && (!isset($s['del']) ? !isset($s['flags']) || ($s['flags'] & $flags) === $flags : $s['del'])) {
            if ($flush) {
                ob_end_flush();
            } else {
                ob_end_clean();
            }
        }
    }

    /** * Marks a response as safe according to RFC8674. * * @see https://tools.ietf.org/html/rfc8674 */
    public function setContentSafe(bool $safe = true): void
    {

        if (!$this->isGuesserSupported()) {
            throw new LogicException(sprintf('The "%s" guesser is not supported.', __CLASS__));
        }

        ob_start();

        // need to use --mime instead of -i. see #6641         passthru(sprintf($this->cmd, escapeshellarg((str_starts_with($path, '-') ? './' : '').$path)), $return);
        if ($return > 0) {
            ob_end_clean();

            return null;
        }

        $type = trim(ob_get_clean());

        if (!preg_match('#^([a-z0-9\-]+/[a-z0-9\-\+\.]+)#i', $type, $match)) {
            // it's not a type, but an error message             return null;
        }

$response->sendResponse();

        $upstream = $filesystem->readStream($path);
        if (!\is_resource($upstream)) {
            throw new RuntimeException(sprintf('Could not open file from: %s', $path));
        }
        $downstream = fopen('php://output', 'wb');
        if (!\is_resource($downstream)) {
            throw new RuntimeException('Could not open temporary stream');
        }

        ob_end_clean();

        while (!feof($upstream)) {
            $read = fread($upstream, 4096);
            if (!\is_string($read)) {
                continue;
            }
            fwrite($downstream, $read);
            flush();
        }
    }

    public function request_filesystem_credentials( $error = false, $context = '', $allow_relaxed_file_ownership = false ) {
        if ( $context ) {
            $this->options['context'] = $context;
        }
        /* * TODO: Fix up request_filesystem_credentials(), or split it, to allow us to request a no-output version. * This will output a credentials form in event of failure. We don't want that, so just hide with a buffer. */
        ob_start();
        $result = parent::request_filesystem_credentials( $error, $context, $allow_relaxed_file_ownership );
        ob_end_clean();
        return $result;
    }

    /** * Retrieves the upgrade messages. * * @since 3.7.0 * * @return string[] Messages during an upgrade. */
    public function get_upgrade_messages() {

break;
            case 'image/webp':
                if (!\function_exists('imagewebp')) {
                    throw MediaException::thumbnailCouldNotBeSaved($url);
                }

                imagewebp($thumbnail, null, $quality);

                break;
        }
        $imageFile = ob_get_contents();
        ob_end_clean();

        try {
            $this->getFileSystem($media)->write($url, (string) $imageFile);
        } catch (\Exception) {
            throw MediaException::thumbnailCouldNotBeSaved($url);
        }
    }

    private function mediaCanHaveThumbnails(MediaEntity $media, Context $context): bool
    {
        if (!$media->hasFile()) {

$_POST[ $key ]      = $_REQUEST[ $key ];
                    $added_input_vars[] = $key;
                }
            }
        }

        // Invoke the widget update callback.         foreach ( (array) $wp_registered_widget_updates as $name => $control ) {
            if ( $name === $parsed_id['id_base'] && is_callable( $control['callback'] ) ) {
                ob_start();
                call_user_func_array( $control['callback'], $control['params'] );
                ob_end_clean();
                break;
            }
        }

        // Clean up any input vars that were manually added.         foreach ( $added_input_vars as $key ) {
            unset( $_POST[ $key ] );
            unset( $_REQUEST[ $key ] );
        }

        // Make sure the expected option was updated.

/* translators: %d: Number of themes being displayed, which cannot currently consider singular vs. plural forms. */
                'announceThemeCount'   => __( 'Displaying %d themes' ),
                /* translators: %s: Theme name. */
                'announceThemeDetails' => __( 'Showing details for theme: %s' ),
            ),
        );

        // Temporarily disable installation in Customizer. See #42184.         $filesystem_method = get_filesystem_method();
        ob_start();
        $filesystem_credentials_are_stored = request_filesystem_credentials( self_admin_url() );
        ob_end_clean();
        if ( 'direct' !== $filesystem_method && ! $filesystem_credentials_are_stored ) {
            $settings['theme']['_filesystemCredentialsNeeded'] = true;
        }

        // Prepare Customize Section objects to pass to JavaScript.         foreach ( $this->sections() as $id => $section ) {
            if ( $section->check_capabilities() ) {
                $settings['sections'][ $id ] = $section->json();
            }
        }

    protected function _loadTranslationData($data, $locale, array $options = array())
    {
        $this->_data = array();
        if (!is_array($data)) {
            if (file_exists($data)) {
                ob_start();
                $data = include($data);
                ob_end_clean();
            }
        }
        if (!is_array($data)) {
            throw new Zend_Translate_Exception("Error including array or file '".$data."'");
        }

        if (!isset($this->_data[$locale])) {
            $this->_data[$locale] = array();
        }

        $this->_data[$locale] = $data + $this->_data[$locale];

            wp_mkdir_p( dirname( $filename ) );
        }

        $result = call_user_func_array( $callback, $arguments );

        if ( $result && $stream ) {
            $contents = ob_get_contents();

            $fp = fopen( $filename, 'w' );

            if ( ! $fp ) {
                ob_end_clean();
                return false;
            }

            fwrite( $fp, $contents );
            fclose( $fp );
        }

        if ( $stream ) {
            ob_end_clean();
        }

$context = $this->env->mergeGlobals($context);
        $level = ob_get_level();
        if ($this->env->isDebug()) {
            ob_start();
        } else {
            ob_start(function D) { return ''; });
        }
        try {
            $this->template->displayBlock($name, $context);
        } catch (\Throwable $e) {
            while (ob_get_level() > $level) {
                ob_end_clean();
            }

            throw $e;
        }

        return ob_get_clean();
    }

    public function displayBlock(string $name, array $context = [])
    {
        $this->template->displayBlock($name, $this->env->mergeGlobals($context));
    }

imagegif($newImage);
                break;
            default:
                imagejpeg($newImage, null, $quality);
                break;
        }

        $content = ob_get_contents();
        if (!\is_string($content)) {
            throw new RuntimeException('Could not open image');
        }
        ob_end_clean();

        $this->mediaService->write($destination, $content);
    }

    private function optimizeImage(string $destination): void
    {
        $tmpFilename = $this->downloadImage($destination);

        try {
            $this->optimizerService->optimize($tmpFilename);
            $this->uploadImage($destination, $tmpFilename);
        }

if (\in_array('~', $call_info['modifiers'], true)) {
            $statics['enabled_mode'] = static::MODE_TEXT;
        }

        $kintstance = static::createFromStatics($statics);
        if (!$kintstance) {
            return 0;
        }

        if (\in_array('-', $call_info['modifiers'], true)) {
            while (\ob_get_level()) {
                \ob_end_clean();
            }
        }

        $kintstance->setStatesFromStatics($statics);
        $kintstance->setStatesFromCallInfo($call_info);

        $trimmed_trace = [];
        $trace = \debug_backtrace();

        foreach ($trace as $frame) {
            if (Utils::traceFrameIsListed($frame, static::$aliases)) {

        $level = ob_get_level();
        if ($this->env->isDebug()) {
            ob_start();
        } else {
            ob_start(function D) { return ''; });
        }
        try {
            $this->display($context);
        } catch (\Throwable $e) {
            while (ob_get_level() > $level) {
                ob_end_clean();
            }

            throw $e;
        }

        return ob_get_clean();
    }

    protected function displayWithErrorHandling(array $context, array $blocks = [])
    {
        try {