Fatal error: Uncaught Error: Call to undefined function SendGrid\mb_strtolower() in /home/opcon/src/composer/vendor/sendgrid/php-http-client/lib/Client.php:620 Stack trace: #0 /home/opcon/src/composer/vendor/sendgrid/php-http-client/examples/example.php(17): SendGrid\Client->__call() #1 {main} thrown in /home/opcon/src/composer/vendor/sendgrid/php-http-client/lib/Client.php on line 620