WP - Optimizations and Cleanup

00_wp-optimizations-n-cleanup.md

** WP - Optimizations and Cleanup **

Here you can find a a list of WP optimization and cleanup functions and methodology.

1. .htaccess

• Force https to your site.
• Enable Browser Cache for your static files. This will fix the "Leverage Browser Caching" in the google pagespeed results.
• Enable file compreassion for faster page load.

2. wp-config.php

• Example of how to enable wp-debug and log the errors, during development.
• Limit posts revisions, in order to have smaller DB.
• Change the update method. /!\ This is usefull usually when bringing a site from server to localhost.

3. functions.php

• Organize your functions.php by including your custom files for better readability. You can seperate you custom files, by responsibility, by back/frond end, by what they modify (e.g. woocommerce mods).

4. cds-wp-admin-tweaks-n-extras.php

• Example custom function to add an extra column to the admin area of the posts list.

5. cds-optimizations-n-tweaks.php

-- Example custom functions for optimizing WP and removing tags for security

• Clean wp_head. Remove unnecessary links, scripts and the_generator (the wp one) from .
• Remove WPML generator.
• Remove Slider Revolution generator.
• Remove Visual Composer / WPBakery Page Builder generator.
• Remove comment-reply.min.js completely.
• Remove jQuery Migrate Script from header and Load jQuery from Google API.
• Remove Yoast SEO comments.
• Remove Query Strings (the version) from script and style files, some files won't be cached if there is a query string in them. /!\ may produce errors! check carefully!
• remove wp version param from any enqueued scripts (using wp_enqueue_script()) or styles (using wp_enqueue_style()).

01_.htaccess

# ##################################
# 	       SECURITY
# ##################################

# Disable the server signature
ServerSignature Off

# Add default charset
AddDefaultCharset UTF-8

# Disable directory browsing
Options All -Indexes

# Redirect all trafic to https
<IfModule mod_rewrite.c>
RewriteEngine On

# Redirect http to https
# RewriteEngine On
# RewriteCond %{HTTPS} !=on
# RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301,NE]

# Redirect www to non-www and http to https
RewriteCond %{HTTPS} off [OR]
RewriteCond %{HTTP_HOST} ^www\. [NC]
RewriteCond %{HTTP_HOST} ^(?:www\.)?(.+)$ [NC]
RewriteRule ^ https://%1%{REQUEST_URI} [L,NE,R=301]

# Redirect non-www to www and http to https
# RewriteCond %{HTTP_HOST} !^www\. [NC,OR]
# RewriteCond %{HTTPS} off
# RewriteCond %{HTTP_HOST} ^(?:www\.)?(.+)$ [NC]
# RewriteRule ^ https://www.%1%{REQUEST_URI} [R=301,L,NE]
</IfModule>

# Protect System Files, Disable PHP in Uploads, Filter Request Methods, by iThemes Security
<IfModule mod_rewrite.c>
	RewriteEngine On

	# Protect System Files
	RewriteRule ^wp-admin/install\.php$ - [F]
	RewriteRule ^wp-admin/includes/ - [F]
	RewriteRule !^wp-includes/ - [S=3]
	RewriteRule ^wp-includes/[^/]+\.php$ - [F]
	RewriteRule ^wp-includes/js/tinymce/langs/.+\.php - [F]
	RewriteRule ^wp-includes/theme-compat/ - [F]
	RewriteCond %{REQUEST_FILENAME} -f
	RewriteRule (^|.*/)\.(git|svn)/.* - [F]

	# Disable PHP in Uploads
	RewriteRule ^wp\-content/uploads/.*\.(?:php[1-7]?|pht|phtml?|phps)\.?$ - [NC,F]

	# Filter Request Methods
	RewriteCond %{REQUEST_METHOD} ^(TRACE|TRACK) [NC]
	RewriteRule ^.* - [F]
</IfModule>

# Secure Important Files
<FilesMatch "^.*(error_log|wp-config\.php|\.ini|\.[hH][tT][aApP].*)$">
Order deny,allow
Deny from all
</FilesMatch>

## Prevent access to specific types of files
#<FilesMatch "\.(htaccess|htpasswd|ini|phps|fla|psd|log|sh)$">
#    Order Allow,Deny
#    Deny from all
#</FilesMatch>

# Protect System Files
<files .htaccess>
	Order allow,deny
	Deny from all
</files>
<files readme.html>
	Order allow,deny
	Deny from all
</files>
<files readme.txt>
	Order allow,deny
	Deny from all
</files>
<files wp-config.php>
	Order allow,deny
	Deny from all
</files>

# Block WordPress xmlrpc.php requests
<Files xmlrpc.php>
order deny,allow
deny from all
</Files>

# Security Headers
# May cause errors, usually when loading external scripts, iframes etc..
<IfModule mod_headers.c>
	# Use HTTP Strict Transport Security to force client to use secure connections only.
	# max-age=15768000 is 6 Months
	Header always set Strict-Transport-Security "max-age=15768000; includeSubDomains; preload"
	
	# Enforce enable the cross-site scripting (XSS) filter built into modern web browsers.
	Header set X-XSS-Protection "1; mode=block"
	
	# Provide clickjacking protection by not allowing iframes to load our website.
	header always set x-frame-options "SAMEORIGIN"
	
	# Prevent IE and Chrome from sniffing a response away from the declared content-type. This helps reduce the danger of drive-by downloads and helps treat the content the right way.
	Header always set x-content-type-options "nosniff"

	# Activate CORS 
    <FilesMatch "\.(ttf|ttc|otf|eot|woff|woff2|font.css|css|js|gif|png|jpe?g|svg|svgz|ico|webp)$">
        Header set Access-Control-Allow-Origin "*"
    </FilesMatch>

    # Set Content security policy as to:
    # default-src 	  - Is the default policy for loading content such as JS, Images, CSS, Fonts etc..
    # https:  		  - Allows loading resources only over HTTPS on any domain.
    # data:  		  - Allows loading resources via the data scheme (eg Base64 encoded images).
    # 'unsafe-inline' - allow inline css,js
    # 'unsafe-eval'   - Allows unsafe dynamic code evaluation such as JavaScript eval()
    # More info: https://content-security-policy.com/
    Header always set Content-Security-Policy "default-src https: data: 'unsafe-inline' 'unsafe-eval'"

    # Set the Referrer-Policy
    # no-referrer-when-downgrade - The origin, path, and querystring of the URL are sent as a referrer when 
    # 							   the protocol security level stays the same or improves,
    #							   but isn't sent to less secure destinations.
    Header set Referrer-Policy "no-referrer-when-downgrade"

    # Set the Feature-policy
	Header set Feature-Policy "vibrate 'self'; push *; camera 'none'; microphone 'none'"
</IfModule>

# ##################################
# 	     PERFORMANCE
# ##################################

# cds - BEGIN DEFLATE COMPRESSION
<IfModule mod_deflate.c>
    # Compress HTML, CSS, JavaScript, Text, XML and fonts
	<IfModule mod_filter.c>
        FilterDeclare COMPRESS
        FilterProvider COMPRESS DEFLATE resp=Content-Type $text/css
        FilterProvider COMPRESS DEFLATE resp=Content-Type $text/html
	 	FilterProvider COMPRESS DEFLATE resp=Content-Type $text/javascript
        FilterProvider COMPRESS DEFLATE resp=Content-Type $text/plain
        FilterProvider COMPRESS DEFLATE resp=Content-Type $text/xml
	 	FilterProvider COMPRESS DEFLATE resp=Content-Type $application/javascript
	 	
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/json
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/x-javascript
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/atom+xml
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/rss+xml
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/xhtml+xml
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/xml
        
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/vnd.ms-fontobject
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/x-font-ttf
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/x-font
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/x-font-opentype
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/x-font-otf
        FilterProvider COMPRESS DEFLATE resp=Content-Type $application/x-font-truetype
        FilterProvider COMPRESS DEFLATE resp=Content-Type $font/opentype
        
        FilterProvider COMPRESS DEFLATE resp=Content-Type $image/svg+xml
        FilterProvider COMPRESS DEFLATE resp=Content-Type $image/x-icon
	 	
        FilterChain COMPRESS
	 	FilterProtocol COMPRESS DEFLATE change=yes;byteranges=no
    </IfModule>
    <IfModule !mod_filter.c>
        # Compress HTML, CSS, JavaScript, Text, XML and fonts
        AddOutputFilterByType DEFLATE application/javascript
        AddOutputFilterByType DEFLATE application/rss+xml
        AddOutputFilterByType DEFLATE application/vnd.ms-fontobject
        AddOutputFilterByType DEFLATE application/x-font
        AddOutputFilterByType DEFLATE application/x-font-opentype
        AddOutputFilterByType DEFLATE application/x-font-otf
        AddOutputFilterByType DEFLATE application/x-font-truetype
        AddOutputFilterByType DEFLATE application/x-font-ttf
        AddOutputFilterByType DEFLATE application/x-javascript
        AddOutputFilterByType DEFLATE application/xhtml+xml
        AddOutputFilterByType DEFLATE application/xml
        AddOutputFilterByType DEFLATE font/opentype
        AddOutputFilterByType DEFLATE font/otf
        AddOutputFilterByType DEFLATE font/ttf
        AddOutputFilterByType DEFLATE image/svg+xml
        AddOutputFilterByType DEFLATE image/x-icon
        AddOutputFilterByType DEFLATE text/css
        AddOutputFilterByType DEFLATE text/html
        AddOutputFilterByType DEFLATE text/javascript
        AddOutputFilterByType DEFLATE text/plain
        AddOutputFilterByType DEFLATE text/xml
    </IfModule>
    # Remove browser bugs (only needed for really old browsers)
    <IfModule mod_setenvif.c>
        BrowserMatch ^Mozilla/4 gzip-only-text/html
	 	BrowserMatch ^Mozilla/4\.0[678] no-gzip
	 	BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
	 	SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-gzip dont-vary
    </IfModule>
    <IfModule mod_headers.c>
        Header append Vary User-Agent env=!dont-vary
	 	Header append Vary Accept-Encoding
    </IfModule>
</IfModule>
# cds - END DEFLATE COMPRESSION

# cds - START EXPIRES CACHING - Optimizing cache-control #
<IfModule mod_expires.c>
    ExpiresActive On
    ExpiresDefault "access plus 1 month"
    ExpiresByType text/html "access plus 1 seconds"
    ExpiresByType text/xml "access plus 1 seconds"
    ExpiresByType text/plain "access plus 1 seconds"
    ExpiresByType application/xml "access plus 1 seconds"
    ExpiresByType application/rss+xml "access plus 1 seconds"
    ExpiresByType application/json "access plus 1 seconds"
    ExpiresByType text/css "access plus 1 month"
    ExpiresByType text/javascript "access plus 1 month"
	ExpiresByType application/javascript "access plus 1 month"
	ExpiresByType application/x-javascript "access plus 1 month"
	ExpiresByType image/x-ico "access plus 1 year"
	ExpiresByType image/x-icon "access plus 1 year"
	ExpiresByType image/gif "access plus 1 year"
	ExpiresByType image/png "access plus 1 year"
	ExpiresByType image/jpe "access plus 1 year"
	ExpiresByType image/jpg "access plus 1 year"
	ExpiresByType image/jpeg "access plus 1 year"
	ExpiresByType video/ogg "access plus 1 month"
	ExpiresByType audio/ogg "access plus 1 month"
    ExpiresByType video/mp4 "access plus 1 month"
    ExpiresByType video/webm "access plus 1 month"
    ExpiresByType font/truetype "access plus 1 month"
    ExpiresByType font/opentype "access plus 1 month"
    ExpiresByType application/x-font-woff "access plus 1 month"
	ExpiresByType image/svg+xml "access plus 1 year"
    ExpiresByType application/pdf "access plus 1 month"
	ExpiresByType application/vnd.ms-fontobject "access plus 1 month"
	<IfModule mod_mime.c>
	 	AddType image/vnd.microsoft.icon .ico
        ExpiresByType image/vnd.microsoft.icon "access plus 1 year"
    </IfModule>
    <IfModule mod_headers.c>
		#  Turn ETags Off
        Header unset ETag
	 	Header unset Pragma
	 	Header unset Last-Modified
		Header set Connection keep-alive
        Header append Cache-Control "public, no-transform, must-revalidate"
    </IfModule>
</IfModule>
# cds - END EXPIRES CACHING - Optimizing cache-control #

## cds - BEGIN Cache-Control Headers
#<ifModule mod_headers.c>
#<filesMatch "\.(ico|jpeg|jpg|png|gif|swf|pdf|svg)$">
#Header set Cache-Control "public"
#</filesMatch>
#<filesMatch "\.(css)$">
#Header set Cache-Control "public"
#</filesMatch>
#<filesMatch "\.(js)$">
#Header set Cache-Control "private"
#</filesMatch>
#<filesMatch "\.(x?html?|php)$">
#Header set Cache-Control "private, must-revalidate"
#</filesMatch>
#</ifModule>
## cds - END Cache-Control Headers

# Now that we're sending far-future expires headers (previous step), 
# we can disable all ETags that otherwise would have been sent by the server
# From: https://htaccessbook.com/disable-etags/
FileETag none

# BEGIN WordPress
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
# END WordPress

01_b_wp-content_uploads_.htaccess

# Block PHP Files in Uploads Directory
<FilesMatch "\.(?i:php)$">
  <IfModule !mod_authz_core.c>
    Order allow,deny
    Deny from all
  </IfModule>
  <IfModule mod_authz_core.c>
    Require all denied
  </IfModule>
</FilesMatch>

02_wp-config.php

<?php
// WP memory settings
// define('WP_MEMORY_LIMIT', '256M');

// Enable debug log in wp-content/debug.log
define('WP_DEBUG', false);
define('WP_DEBUG_LOG', false);
define('WP_DEBUG_DISPLAY', false);

// Limit revisions to 3
define('WP_POST_REVISIONS', 3);

// OR 
// Disable revisions
// define('WP_POST_REVISIONS', false);

// Require SSL for Admin and Logins
define( 'FORCE_SSL_ADMIN', true );

// Disable the Plugin and Theme Editor
define( 'DISALLOW_FILE_EDIT', true );

// Block external URL requests by defining WP_HTTP_BLOCK_EXTERNAL as true and this will only allow localhost and your blog to make requests
define( 'WP_HTTP_BLOCK_EXTERNAL', true );
// define( 'WP_ACCESSIBLE_HOSTS', 'api.wordpress.org,*.github.com' ); //comma separated list of hostnames to allow, wildcard domains are supported

// Solve problem of wordpress asking for ftp 
// when updating plugins in localhost
// define('FS_METHOD','direct');

03_functions.php

<?php 

/************************************************************************
 * load Optimization file, which has various 
 * functions to improve pagespeed of the site
 * and cleanup WP
 ***********************************************************************/
include( get_stylesheet_directory() . './cds-optimizations-n-tweaks.php' );

/************************************************************************
 * load cds-wp-admin-tweaks-n-extras file, which has various 
 * functions to make changes/additions to the WP admin area
 ***********************************************************************/
include( get_stylesheet_directory() . './cds-wp-admin-tweaks-n-extras.php' );

04_cds-optimizations-n-tweaks.php

<?php
/**
 * CubeDesigns - Wordpress Optimizations and Tweaks
 *
 * Some of the below function are from the Plugin: Meta Generator and Version Info Remover
 * (https://wordpress.org/plugins/meta-generator-and-version-info-remover/)
 */


/************************************************************************
 * Header items cleaning.
 *
 * @return void
 ***********************************************************************/
function cds_clean_the_header_outout() {
    remove_action( 'wp_head', 'wp_generator' ); // Remove WP Generator Vesion.
    remove_action( 'wp_head', 'wp_resource_hints', 2 ); // Remove s.w.org DNS-Prefetch.
    remove_action( 'wp_head', 'wlwmanifest_link' ); // Remove wlwmanifest.xml.
    remove_action( 'wp_head', 'rsd_link' ); // Remove Really Simple Discovery Link.
    remove_action( 'wp_head', 'wp_shortlink_wp_head', 10, 0 ); // Remove Shortlink URL.
    remove_action( 'wp_head', 'print_emoji_detection_script', 7 ); // Remove Emoji's Styles and Scripts.
    remove_action( 'wp_print_styles', 'print_emoji_styles' ); // Remove Emoji's Styles and Scripts.
    remove_action( 'admin_print_scripts', 'print_emoji_detection_script' ); // Remove Emoji's Styles and Scripts from Admin.
    remove_action( 'admin_print_styles', 'print_emoji_styles' ); // Remove Emoji's Styles and Scripts from Admin.
    remove_action( 'wp_head', 'index_rel_link' ); // Remove Link to Home Page.
    remove_action( 'wp_head', 'feed_links_extra', 3 ); // Remove Every Extra Links to RSS Feeds.
    remove_action( 'wp_head', 'adjacent_posts_rel_link_wp_head', 10 ); // Remove Prev-Next Links from Header - Not from Post.
    remove_action( 'wp_head', 'adjacent_posts_rel_link', 10, 0 ); // Remove Prev-Next Links.
    remove_action( 'wp_head', 'start_post_rel_link', 10, 0 ); // Remove Random Link Post.
    remove_action( 'wp_head', 'parent_post_rel_link', 10, 0 ); // Remove parent Post Link.

    add_filter( 'the_generator', '__return_false' ); // Remove Generator Name from RSS Feed.
}
add_action( 'after_setup_theme', 'cds_clean_the_header_outout' );


/************************************************************************
 * Remove WPML generator
 ***********************************************************************/
if ( !empty ( $GLOBALS['sitepress'] ) ) {
    function cds_remove_wpml_generator() {
        remove_action(
            current_filter(),
            array ( $GLOBALS['sitepress'], 'meta_generator_tag' )
        );
    }
    add_action( 'wp_head', 'cds_remove_wpml_generator', 0 );
}


/************************************************************************
 * Remove Slider Revolution generator
 ***********************************************************************/
function cds_remove_revslider_meta_tag() {
    return '';
}
add_filter( 'revslider_meta_generator', 'cds_remove_revslider_meta_tag' );


/************************************************************************
 * Remove Visual Composer / WPBakery Page Builder generator
 ***********************************************************************/
function cds_remove_visual_composer_generator() {
    if ( class_exists( 'Vc_Manager' ) || class_exists( 'Vc_Base' ) ) {
        remove_action('wp_head', array(visual_composer(), 'addMetaData'));
    }
}
add_action('init', 'cds_remove_visual_composer_generator', 100);


/************************************************************************
 * Remove comment-reply.min.js completely
 ***********************************************************************/
function cds_remove_comment_reply_js() {
	wp_deregister_script( 'comment-reply' );
}
add_action('init', 'cds_remove_comment_reply_js', 10);


/************************************************************************
 * Remove jQuery Migrate Script from header 
 * and Load jQuery from Google API
 ***********************************************************************/
function cds_remove_jquery_migrate_load_google_hosted_jquery(){
	if (!is_admin()) {
		wp_deregister_script('jquery');
		wp_register_script('jquery', 'https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js', false, null);
		wp_enqueue_script('jquery');
	}
}
add_action('init','cds_remove_jquery_migrate_load_google_hosted_jquery');


/************************************************************************
 * Remove Yoast SEO comments
 ***********************************************************************/
function cbs_remove_yoast_seo_comments() {
    if ( ! class_exists( 'WPSEO_Frontend' ) ) {
        return;
    }
    $instance = WPSEO_Frontend::get_instance();
    // To ensure that future version of the plugin does not cause any problem
    if ( ! method_exists( $instance, 'debug_mark') ) {
        return;
    }
    remove_action( 'wpseo_head', array( $instance, 'debug_mark' ), 2 );
}
add_action('template_redirect', 'cbs_remove_yoast_seo_comments', 9999);

add_filter('wpseo_debug_markers', '__return_false', 9999); // Requires Yoast > v14.0 

/************************************************************************
 * Remove Query Strings (the version) from script and style files,
 * some files won't be cached if there is a query string in them
 ***********************************************************************/
// function cds_remove_script_version( $src ){
//     $parts = explode( '?ver', $src );
//     return $parts[0];
// }
// add_filter( 'script_loader_src', 'cds_remove_script_version', 15, 1 );
// add_filter( 'style_loader_src', 'cds_remove_script_version', 15, 1 );


/************************************************************************
 * remove wp version param from any enqueued scripts 
 * (using wp_enqueue_script()) or styles (using wp_enqueue_style()).
 ***********************************************************************/
function cds_remove_appended_version_script_style( $target_url ) {
    $filename_arr = explode('?', basename($target_url));
    $filename = $filename_arr[0];

    /* check if "ver=" argument exists in the url or not */
    if (strpos( $target_url, 'ver=' )) {
        $target_url = remove_query_arg( 'ver', $target_url );
    }
    /* check if "version=" argument exists in the url or not */
    if (strpos( $target_url, 'version=' )) {
        $target_url = remove_query_arg( 'version', $target_url );
    }
    return $target_url;
}
/**
 * Priority set to 20000. Higher numbers correspond with later execution.
 * Hook into the style loader and remove the version information.
 */
add_filter('style_loader_src', 'cds_remove_appended_version_script_style', 20000);
/**
 * Hook into the script loader and remove the version information.
 */
add_filter('script_loader_src', 'cds_remove_appended_version_script_style', 20000);

05_cds-wp-admin-tweaks-n-extras.php

<?php
/**
 * CubeDesigns - Wordpress Admin Tweaks and Extras
 *
 */



/************************************************************************
 * Add and Display featured image column in Posts list 
 ***********************************************************************/
function cds_add_featured_image_column( $columns ) {
    $columns['featured_image_thumb'] = 'Featured Image';
    return $columns;
}
add_filter('manage_posts_columns' , 'cds_add_featured_image_column', 5);

function cds_display_featured_image_column_data( $column, $post_id ) {
    switch ( $column ) {
        case 'featured_image_thumb':
            echo get_the_post_thumbnail($post_id, 'thumbnail');
            break;
    }
}
add_action( 'manage_posts_custom_column' , 'cds_display_featured_image_column_data', 5, 2 ); 

06_clean_wp_expired_sessions.php

if ( current_user_can( 'manage_options' ) && get_current_user_id() == 2 ) {
    global $wpdb;
    
    //  Get expired wp_sessions *use LIMIT if you have a LOT of wp_sessions
    $expiration_keys = $wpdb->get_results( "
        SELECT option_name, option_value 
        FROM $wpdb->options 
        WHERE option_name LIKE '_wp_session_expires_%' 
        AND option_value < NOW() 
        LIMIT 0, 50000
    " );
  
	$now = time(); // EPOCH time
	$expired_sessions = array();

	foreach( $expiration_keys as $expiration ) {
		// Double check that the session has expired
		if ( $now > intval( $expiration->option_value ) ) {
			// Get the session ID by parsing the option_name
			$session_id = str_replace("_wp_session_expires_", "", $expiration->option_name);

			$expired_sessions[] = $expiration->option_name;
			$expired_sessions[] = "_wp_session_$session_id";
		}
	}

	// Delete all expired sessions in a single query
	if ( ! empty( $expired_sessions ) ) {
		$option_names = implode( "','", $expired_sessions );
    // highlight_string("<?php\n\$option_names =\n" . var_export($option_names) . ";\n");
		$wpdb->query( "DELETE FROM $wpdb->options WHERE option_name IN ('$option_names')" );

	}
    
}

07_varius_extra_functions.php

<?php
/**
 * CubeDesigns - Varius functions for specific cases 
 *
 */


/**
 * [cds_clean_attached_image_attrs]
 * 
 * Remove srcset and sizes in specific page
 * 
 * @param  [type] $attr       [description]
 * @param  [type] $attachment [description]
 * @param  [type] $size       [description]
 * @return [type]             [description]
 */
function cds_clean_attached_image_attrs( $attr, $attachment, $size ) {
	// Limit to specific page. e.g. posts grid page with lots of images
    // If page is: #some_page_id
	if ( is_page(137) ) {
	    // highlight_string("<?php\n\$attr =\n" . var_export($attr, true) . ";\n");
        // Remove srcset and sizes
        if ( isset($attr["srcset"]) ) { unset($attr["srcset"]); }
        if ( isset($attr["sizes"]) ) { unset($attr["sizes"]); }
    }
    return $attr;
}
add_filter( 'wp_get_attachment_image_attributes', 'cds_clean_attached_image_attrs', 10, 3 );


/**
 * [cds_disable_wp_responsive_images]
 * 
 * disable srcset on frontend
 * 
 * @return [type] [description]
 */
function cds_disable_wp_responsive_images() {
	return 1;
}
add_filter('max_srcset_image_width', 'cds_disable_wp_responsive_images');


/**
 * [cds_style_loader_tag_filter]
 * Add display=swap to google fonts, when not having access to the creation enque style
 *
 * @return the modified <link> tag
 */
add_filter('style_loader_tag', 'cds_style_loader_tag_filter', 10, 2);
function cds_style_loader_tag_filter($html, $handle) {
    // add &display=swap in google fonts Roboto
    if ($handle === 'Roboto') {
        if ( function_exists('simplexml_load_file') ) {
            $xmlFromHtml = simplexml_load_string($html);
            $hrefs = $xmlFromHtml->xpath("//@href");
		
            if (isset($hrefs) && !empty($hrefs) && is_array($hrefs)) {
                foreach($hrefs as $href) {
                    $modified_href = (string)$href . '&display=swap';
                    $final_link = "<link rel='stylesheet' id='Roboto-css' href='" . $modified_href . "' type='text/css' media='all' />";
                    $html = $final_link;
                    break;
                }
            }
        }
    }
    return $html;
}