Magento – Unsupported declare ‘strict_types’ in Magento 2.3.0

composermagento2magento2.3.0

Error : Unsupported declare strict_types in
../vendor/magento/inventory-composer-installer while install the extension using composer in Magento 2.3.0.

Best Answer

I had the same issue, it is due to the version of PHP you are using, and the version of PHP required for Composer.

My CLI was using PHP 5.4, but I had to run it on 7.2.

So instead of running something like:

composer upgrade

I ran:

php7.2 /path/to/composer upgrade

Hope this helps. I was confused on this for a little while, as the error doesn't seem related to the PHP version, but seems like more of a bug with the installation.

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