(In reply to comment #0)

Is PHP 5.4.0 or higher required?

No it isn't. It should be 5.3.2, though it does look code unconditionally uses code from PHP 5.4:

/**

• Don't escape /.
• Available since PHP 5.4.0.
• @link http://php.net/manual/en/json.constants.php */

define ('JSON_UNESCAPED_SLASHES', 64);

Caused by https://gerrit.wikimedia.org/r/#/c/50140/

(In reply to comment #0)

I use PHP 5.4.11 but I get the error message above. Where is the error?

If you're using 5.4.11, then the 5.3 versus 5.4 issue isn't what's affecting you.

Do you have the json extension disabled, perhaps?

Now I installed the packet php-json (ftp://ftp.cygwinports.org/pub/cygwinports/release-2/PHP/php/php-json/) and now it works again.

Since people can compile php with and without certain extensions, perhaps we should extend the conditional beyond the PHP version and also check that that json extension is in fact installed?

A simple function_exists( 'json_encode' ) should suffice. Or perhaps defined( 'JSON_PRETTY_PRINT' ) if we want to worry about the version of the extension as well.

(In reply to comment #4)

Since people can compile php with and without certain extensions, perhaps we
should extend the conditional beyond the PHP version and also check that that
json extension is in fact installed?

And do what, exactly, if not?

It would be nice to have a checker which checks all required packages/extensions/functions. This checker should run on installation and on the fatal error exception error page.

(In reply to comment #6)

It would be nice to have a checker which checks all required
packages/extensions/functions. This checker should run on installation and on
the fatal error exception error page.

Filed as bug 47564.