Magento 2.3 has dropped support for PHP 7.0 since 2018-03-01

dmitry_fedyuk (Dmitrii Fediuk) April 16, 2018, 1:27pm 1

https://github.com/magento/magento2/blob/524f4b8e/composer.json#L15-L15

https://github.com/magento/magento2/commit/524f4b8e

Magento 2.3 became compatible with PHP 7.2 since 2018-03-01

dmitry_fedyuk (Dmitrii Fediuk) April 16, 2018, 1:28pm 2

See also:

Magento 2.3 became compatible with PHP 7.2 since 2018-03-01