Error session_start() expects parameter 1

Hi guys

I have switched to 7.0 PHP version today and I have noticed that line showing above the blog header (frontend)

Warning: session_start() expects parameter 1 to be array, string given in /wp-includes/class-wp-hook.php on line 288

apart from that in the backend I have this:

Warning: session_start() expects parameter 1 to be array, string given in /wp-includes/class-wp-hook.php on line 288

Warning: Cannot modify header information – headers already sent by (output started at /wp-includes/class-wp-hook.php:288) in /wp-includes/functions.php on line 5946

Warning: Cannot modify header information – headers already sent by (output started at /wp-includes/class-wp-hook.php:288) in /wp-admin/includes/misc.php on line 1252

Warning: Cannot modify header information – headers already sent by (output started at /wp-includes/class-wp-hook.php:288) in /wp-admin/admin-header.php on line 9

What to do?
—

class-wp-hook.php:288 is this:
$value = call_user_func_array( $the_[‘function’], $args );