/libraries/src/Exception/ExceptionHandler.php on line 37 looks good to me

That's the 3.9 line @PhilETaylor. In 4.0 line 37 is a method declaration which uses PHP 7 scalar and return typehints.

@ghazal Make sure your CLI PHP binary is running the expected version (as web and CLI can be running two different PHP versions).

In that case maybe the CLI code needs to be doing a PHP Version sanity check before running commands?

ffc8f3b adds the PHP version check and minimum PHP constant to the cli/joomla.php script.

:-)

... Make sure your CLI PHP binary is running the expected version (as web and CLI can be running two different PHP versions).
That's what I suspected.
My computer runs on PHP 5.6.30
My bitnami stack on PHP 7.2.5
The joomla package reads PHP 5.6.30
If I update composer.json to PHP 7.2.5 (having removed composer.lock before) and run
composer install again, the joomla package reads PHP 7.2.5 allright.
But the php whatever command still throws that error.
I guess I'll have to follow your advice (check CLI PHP binary) or maybe update the php version on this computer.

Thanks for your replies.

@ghazal Please close issue if resolved.

Not really resolved, but OK. I'll reopen it if necessary.

Finally, I used this binary package to update my global PHP version :
https://php-osx.liip.ch/

Symfony is grumbling now.

"I'll get it one day, I'll get it."

If you are on a mac, checkout the Homebrew implementation of PHP which allows easy installation of multiple versions of PHP and the ability to switch between them.

see the PHP section of https://getgrav.org/blog/macos-mojave-apache-multiple-php-versions which explains how.

@PhilETaylor
Thanks.
I use Homebrew but have been stumped by their recent deprecation of php tap.
Gonna test this tut.

yeah that was a pain in the arse... but it all seems to be stable again now.

@ghazal can this Issue be closed?

Yes.

thanks @ghazal