header - PHP code example

PHP Function Header - How to Leverage It in Your Code

The php function header is one of the most powerful features in the language, allowing developers to manipulate HTTP headers and control communication between the web server and client. This is essential for improving the functionality and user experience of web applications. In this article, we will explore the different use cases of this function and show how to leverage it in your code.

The header() function in PHP allows you to send a raw HTTP header. It must be called before any other output is sent, whether it be through normal HTML tags, blank lines or from other functions such as print or echo. It’s common for errors to be caused if the function is called after other output is sent, so it’s important that you call it before any output is produced.

In addition to modifying headers, the header() function can also be used to send status codes to the browser. This can be useful in scenarios such as when a form submission is successful, when users need to be authenticated or when pages have been permanently moved to another URL.

The header() function can also be used to set cache-control headers. This is useful for preventing caching of web pages, especially when they have dynamic content or are updated frequently. Setting these headers will override any caching options that the end-user may have set in their browser, ensuring that the latest version of the page is always being sent to the browser.

header example

$load = $_GET['load'];
if ( is_array( $load ) ) {
    ksort( $load );
    $load = implode( '', $load );
}

$load = preg_replace( '/[^a-z0-9,_-]+/i', '', $load );
$load = array_unique( explode( ',', $load ) );

if ( empty( $load ) ) {
    header( "$protocol 400 Bad Request" );
    exit;
}

require ABSPATH . 'wp-admin/includes/noop.php';
require ABSPATH . WPINC . '/script-loader.php';
require ABSPATH . WPINC . '/version.php';

$expires_offset = 31536000; // 1 year. $out            = '';

$wp_scripts = new WP_Scripts();

// Install all applicable language packs for the plugin.             $lp_upgrader->bulk_upgrade( $language_packs );
        }

        $path          = WP_PLUGIN_DIR . '/' . $file;
        $data          = get_plugin_data( $path, false, false );
        $data['_file'] = $file;

        $response = $this->prepare_item_for_response( $data, $request );
        $response->set_status( 201 );
        $response->header( 'Location', rest_url( sprintf( '%s/%s/%s', $this->namespace, $this->rest_base, substr( $file, 0, - 4 ) ) ) );

        return $response;
    }

    /** * Checks if a given request has access to update a specific plugin. * * @since 5.5.0 * * @param WP_REST_Request $request Full details about the request. * @return true|WP_Error True if the request has access to update the item, WP_Error object otherwise. */

            } else {
                $otherCookies[] = $h;
            }
        }
        if (null === $sessionCookie) {
            return null;
        }

        header_remove('Set-Cookie');
        foreach ($otherCookies as $h) {
            header($h, false);
        }

        return $sessionCookie;
    }
}

        $image = apply_filters_deprecated( 'image_save_pre', array( $image, $attachment_id ), '3.5.0', 'image_editor_save_pre' );

        switch ( $mime_type ) {
            case 'image/jpeg':
                header( 'Content-Type: image/jpeg' );
                return imagejpeg( $image, null, 90 );
            case 'image/png':
                header( 'Content-Type: image/png' );
                return imagepng( $image );
            case 'image/gif':
                header( 'Content-Type: image/gif' );
                return imagegif( $image );
            case 'image/webp':
                if ( function_exists( 'imagewebp' ) ) {
                    header( 'Content-Type: image/webp' );
                    return imagewebp( $image, null, 90 );
                }

$replace = 0 === strcasecmp($name, 'Content-Type');

                if (null !== $previousValues && array_diff($previousValues, $values)) {
                    header_remove($name);
                    $previousValues = null;
                }

                $newValues = null === $previousValues ? $values : array_diff($values, $previousValues);
            }

            foreach ($newValues as $value) {
                header($name.': '.$value, $replace, $this->statusCode);
            }

            if ($informationalResponse) {
                $this->sentHeaders[$name] = $values;
            }
        }

        // cookies         foreach ($this->headers->getCookies() as $cookie) {
            header('Set-Cookie: '.$cookie, false, $this->statusCode);
        }

function wp_check_php_mysql_versions() {
    global $required_php_version, $wp_version;

    $php_version = PHP_VERSION;

    if ( version_compare( $required_php_version, $php_version, '>' ) ) {
        $protocol = wp_get_server_protocol();
        header( sprintf( '%s 500 Internal Server Error', $protocol ), true, 500 );
        header( 'Content-Type: text/html; charset=utf-8' );
        printf(
            'Your server is running PHP version %1$s but WordPress %2$s requires at least %3$s.',
            $php_version,
            $wp_version,
            $required_php_version
        );
        exit( 1 );
    }

    // This runs before default constants are defined, so we can't assume WP_CONTENT_DIR is set yet.

        do_action( 'rest_after_insert_attachment', $attachment, $request, true );

        wp_after_insert_post( $attachment, false, null );

        if ( defined( 'REST_REQUEST' ) && REST_REQUEST ) {
            /* * Set a custom header with the attachment_id. * Used by the browser/client to resume creating image sub-sizes after a PHP fatal error. */
            header( 'X-WP-Upload-Attachment-ID: ' . $attachment_id );
        }

        // Include media and image functions to get access to wp_generate_attachment_metadata().         require_once ABSPATH . 'wp-admin/includes/media.php';
        require_once ABSPATH . 'wp-admin/includes/image.php';

        /* * Post-process the upload (create image sub-sizes, make PDF thumbnails, etc.) and insert attachment meta. * At this point the server may run out of resources and post-processing of uploaded images may fail. */
        wp_update_attachment_metadata( $attachment_id, wp_generate_attachment_metadata( $attachment_id, $file ) );

    if ( ! $path || ! @is_file( $path ) ) {
        return false;
    }

    return @file_get_contents( $path );
}

$expires_offset = 31536000; // 1 year.
header( 'Content-Type: application/javascript; charset=UTF-8' );
header( 'Vary: Accept-Encoding' ); // Handle proxies. header( 'Expires: ' . gmdate( 'D, d M Y H:i:s', time() + $expires_offset ) . ' GMT' );
header( "Cache-Control: public, max-age=$expires_offset" );

$file = get_file( $basepath . '/wp-tinymce.js' );
if ( isset( $_GET['c'] ) && $file ) {
    echo $file;
} else {
    // Even further back compat.     echo get_file( $basepath . '/tinymce.min.js' );
    echo get_file( $basepath . '/plugins/compat3x/plugin.min.js' );
}

<?php /** * Database Repair and Optimization Script. * * @package WordPress * @subpackage Database */
define( 'WP_REPAIRING', true );

require_once dirname( dirname( __DIR__ ) ) . '/wp-load.php';

header( 'Content-Type: text/html; charset=utf-8' );
?> <!DOCTYPE html> <html <?php language_attributes(); ?>> <head> <meta name="viewport" content="width=device-width" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta name="robots" content="noindex,nofollow" /> <title><?php _e( 'WordPress &rsaquo; Database Repair' ); ?></title> <?php wp_admin_css( 'install', true ); ?> </head> <body class="wp-core-ui"> <p id="logo"><a href="

        // display or fetch         if ($display) {
            if ($this->caching && $this->cache_modified_check) {
                $_isCached = $_template->isCached() && !$_template->has_nocache_code;
                $_last_modified_date = @substr($_SERVER['HTTP_IF_MODIFIED_SINCE'], 0, strpos($_SERVER['HTTP_IF_MODIFIED_SINCE'], 'GMT') + 3);
                if ($_isCached && $_template->cached->timestamp <= strtotime($_last_modified_date)) {
                    switch (PHP_SAPI) {
                        case 'cgi':         // php-cgi < 5.3                         case 'cgi-fcgi':    // php-cgi >= 5.3                         case 'fpm-fcgi':    // php-fpm >= 5.3.3                         header('Status: 304 Not Modified');
                        break;

                        case 'cli':
                        if (/* ^phpunit */!empty($_SERVER['SMARTY_PHPUNIT_DISABLE_HEADERS'])/* phpunit$ */) {
                            $_SERVER['SMARTY_PHPUNIT_HEADERS'][] = '304 Not Modified';
                        }
                        break;

                        default:
                        header($_SERVER['SERVER_PROTOCOL'].' 304 Not Modified');
                        break;
                    }

<?php /** * RSS2 Feed Template for displaying RSS2 Posts feed. * * @package WordPress */

header( 'Content-Type: ' . feed_content_type( 'rss2' ) . '; charset=' . get_option( 'blog_charset' ), true );
$more = 1;

echo '<?xml version="1.0" encoding="' . get_option( 'blog_charset' ) . '"?' . '>';

/** * Fires between the xml and rss tags in a feed. * * @since 4.0.0 * * @param string $context Type of feed. Possible values include 'rss2', 'rss2-comments', * 'rdf', 'atom', and 'atom-comments'. */

if ($localFilesyste->checksum('shopware.php') != $remoteFilesyste->checksum('shopware.php')) {
            throw new RuntimeException('Filesytems does not seem to match');
        }
    }

    /** * @param int $code * @param array $data */
    private function toJson($code, $data)
    {
        $this->response->header('Content-Type', 'application/json');
        $this->response->status($code);

        if (\defined('JSON_PRETTY_PRINT')) {
            $this->response->body(json_encode($data, JSON_PRETTY_PRINT));
        } else {
            $this->response->body(json_encode($data));
        }
    }
}

$this->init();
        $this->bulk = true;
        $this->upgrade_strings();

        $current = get_site_transient( 'update_themes' );

        add_filter( 'upgrader_pre_install', array( $this, 'current_before' ), 10, 2 );
        add_filter( 'upgrader_post_install', array( $this, 'current_after' ), 10, 2 );
        add_filter( 'upgrader_clear_destination', array( $this, 'delete_old_theme' ), 10, 4 );

        $this->skin->header();

        // Connect to the filesystem first.         $res = $this->fs_connect( array( WP_CONTENT_DIR ) );
        if ( ! $res ) {
            $this->skin->footer();
            return false;
        }

        $this->skin->bulk_header();

        /* * Only start maintenance mode if: * - running Multisite and there are one or more themes specified, OR * - a theme with an update available is currently in use. * @todo For multisite, maintenance mode should only kick in for individual sites if at all possible. */

<?php declare(strict_types=1);

$uri = $_SERVER['REQUEST_URI'] ?? '/v1/release/update';
$fileName = __DIR__ . '/update.zip';

if (str_starts_with($uri, '/swplatform/autoupdate')) {
    header('Content-Type: application/json');
    echo json_encode([]);
    exit;
}

if (str_starts_with($uri, '/v1/release/update')) {
    header('Content-Type: application/json');
    echo json_encode([
        'version' => '6.5.0.0',
        'release_date' => false,
        'security_update' => false,
        'uri' => 'http://localhost:8060/update.zip',

$encoding[] = 'UTF-8';
        }
        return $encoding;
    }

    public static function output_javascript()
    {
        if (function_exists('ob_gzhandler'))
        {
            ob_start('ob_gzhandler');
        }
        header('Content-type: text/javascript; charset: UTF-8');
        header('Cache-Control: must-revalidate');
        header('Expires: ' . gmdate('D, d M Y H:i:s', time() + 604800) . ' GMT'); // 7 days         ?> function embed_quicktime(type, bgcolor, width, height, link, placeholder, loop) { if (placeholder != '') { document.writeln('<embed type="'+type+'" style="cursor:hand; cursor:pointer;" href="'+link+'" src="'+placeholder+'" width="'+width+'" height="'+height+'" autoplay="false" target="myself" controller="false" loop="'+loop+'" scale="aspect" bgcolor="'+bgcolor+'" pluginspage="http://www.apple.com/quicktime/download/"></embed>'); } else { document.writeln('<embed type="'+type+'" style="cursor:hand; cursor:pointer;" src="'+link+'" width="'+width+'" height="'+height+'" autoplay="false" target="myself" controller="true" loop="'+loop+'" scale="aspect" bgcolor="'+bgcolor+'" pluginspage="http://www.apple.com/quicktime/download/"></embed>'); } } function embed_flash(bgcolor, width, height, link, loop, type) { document.writeln('<embed src="'+link+'" pluginspage="http://www.macromedia.com/go/getflashplayer" type="'+type+'" quality="high" width="'+width+'" height="'+height+'" bgcolor="'+bgcolor+'" loop="'+loop+'"></embed>'); } function embed_flv(width, height, link, placeholder, loop, player) { document.writeln('<embed src="'+player+'" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" quality="high" width="'+width+'" height="'+height+'" wmode="transparent" flashvars="file='+link+'&autostart=false&repeat='+loop+'&showdigits=true&showfsbutton=false"></embed>'); } function embed_wmedia(width, height, link) { document.writeln('<embed type="application/x-mplayer2" src="'+link+'" autosize="1" width="'+width+'" height="'+height+'" showcontrols="1" showstatusbar="0" showdisplay="0" autostart="0"></embed>'); }