Trouble after update

Just updated my wp and got the “Blank page” Have tried everything but it doesn’t seam to work with the usual tricks to get it sorted. Now I have a :

Fatal error: Call to undefined function wp_json_encode() in /customers/d/0/1/jika-tabi.se/httpd.www/wp-includes/class.wp-scripts.php on line 186

What to do please… Im lost ?

Thank you