You should not be executing anything before your DOCTYPE tag. That will all be invalid code and is also the issue leading to your error.
In general, any output like above should be done after the <head></head> tags, although some prefer to hook into the wp_head hook to execute functions like your code. I do prefer however to move such code after the closing head tag.
So your solution would be to move your conditional code to just after the closing head tag
Related Posts:
- create a button in the header of the mobile menu in the middle of the logo and the menu accordion
- How to hide or change mobile header logo with Additional CSS or custom PHP
- What is the difference between “SMS Push” and “WAP Push”?
- Proper usage of wp_is_mobile()?
- How do I make my blog iPad / iPhone / Android friendly?
- WordPress REST endpoint with JSON for Mobile App integration
- WordPress on WP7
- Developing mobile version of WordPress site
- How can i disable a plugin for a mobile phone?
- How can I make a wp site in a mobile application?
- Mobile Menu Not Showing
- Create mobile navigation header with settings integration
- Querying custom fields with Carrington mobile theme
- Is there any mobile application for WordPress? [closed]
- detect screen width in functions
- A URL that links specifically to the mobile version of my site?
- How to disable/enable specific plugins for a mobile theme?
- Elements floating on top of each other when Resizing or checking site on mobile. Twenty Twelve
- Mobile theme not showing correct page after custom re-writes
- My website is not responsive on mobile devices
- Best method for loading content on mobile – issue with wp_is_mobile
- Why is only one page responsive? [closed]
- Strategy for making a mobile version of an existing site? [closed]
- How can I redirect mobile users to diff url, but also allow them to come back to full site
- Open Menu is not working in Mobile view [closed]
- WordPress website loads fine on desktop browsers but Safari for iOS cannot load it completely [closed]
- Static page for desktop or mobile
- $is_iphone – to redirect a page
- Quick login from mobile phone
- How can I use my blog page as the homepage but only for mobile/tablet visits?
- Dropdown menu not displaying in handheld slide menu effect
- How to disable the topbar in mobile? [closed]
- WordPress mobil will not scroll
- Disable rendering of objects on mobile/above certain screen resolution
- Adapting “wide with” Gutenberg blocks for mobile
- Close Mobile Slide Menu on Click
- How can I hide/show text only for mobile users?
- Different Home page for Mobile without changing URL
- App in wordpress doesnt fit to mobile screen
- Add audio post from smartphone
- Display posts on a map
- responsive website
- Mobile Menu not working on TwentyThirteen child theme
- change theme when on mobile and also on Ipad portrait view
- Subdomain for WP Mobile Edition and Cloudfare
- How can I stop Jetpack mobile theme from using full size featured images?
- website is viewing as mobile, how do I turn this off?
- Work on two different themes at the same time in wordpress
- How to disable fancybox on small screens
- Add exception to WP Mobile Detector
- Using WordPress as a Mobile App Backend
- WordPress Mobile Edition not working with WP v3.5
- Why doesn’t the mobile version of my website take updates?
- Links not showing up on “AMPforWP”
- Viewing a WordPress website in landscape [closed]
- different startsite for IOS and change menu
- wordpress fancybox responsive mobile or pc version [closed]
- Separate Mobile site
- Not able to see updates my mobile after making updates on wordpress mobile version
- Not working Mobile view and Desktop view properly when we searched on website
- Mobile App Not Posting, Debugging Options
- Vertical scrolling is not stopping correctly in Mobile and Desktop
- WordPress blogsite logo is different on my computer and mobile
- mobile menu is not showing
- How do I enable automatic stacking for mobile?
- @Media min-width & max-width
- How to print to the console in Android Studio?
- How can I edit a .jar file?
- What is the best way to detect a mobile device?
- How to detect mobile devices and present them a specific theme?
- Disable plugin / plugin action via theme
- Is wp_is_mobile() effective?
- Excluding iPad from wp_is_mobile
- Building a custom REST API
- Create mobile site with same content just different theme
- What’s the best way to use the Featured Image for responsive web design?
- How can i get the name parameter defined in get_header?
- WP Multisite: load content from site X on site Y
- wordpress json custom taxonomy problem
- How to get the custom header image’s alt text?
- When cropping a header image, retain meta data (i.e. name, description, etc.) from original image?
- How-to make the admin area mobile friendly [closed]
- How to stop mobile theme inheriting desktop navigation menu?
- How can I have two different urls for the same page that load two different templates?
- How-to add rewrite rules to point the uploads folder to a subdomain
- Add Useragent to the body class?
- Adding custom fields to the header.php
- Deactivate plugins only for mobile devices
- What’s the earliest point I can get the queried object ID?
- Additional Option on Custom Header admin
- Using a Theme inside a Plugin directory
- How to get a different mobile menu than desktop menu in the twentytwelve child theme
- How to include one class/instance without using global variables
- WP Super Cache separate cache for mobile
- How to edit codes of an individual page/post?
- Change the default number of posts to show on mobile version
- Custom text-only header
- How can I add a custom header to a custom template in a plugin without using the theme folders
- Ajax template: how to handle head section
- Load a theme based on browser detection