Cron Archiving Error - PHP Warning: Unexpected character in input: '\'... (no replies)

I've set up a cron job for archiving. PHP version is 5.3.24. The command works when I run it outside of cron. But the cron job gives me this message:

Error in the last Piwik archive.php run: 
The Piwik URL https://[domain]/index.php does not seem to be pointing to a Piwik server. Response was ''.


 Here is the full errors output:

---------------------------
INIT
Piwik is installed at: https://[domain]/index.php
Running Piwik 2.2.0 as Super User
ERROR: Got invalid response from API request: https://[domain]/index.php?module=API&method=API.getDefaultMetricTranslations&format=original&serialize=1&trigger=archivephp. Response was 'PHP Warning:  Unexpected character in input:  '\' (ASCII=92) state=1 in /path/to/piwik/console on line 20
PHP Parse error:  syntax error, unexpected T_STRING in /path/to/piwik/console on line 20
'

Any idea what could cause this?

PS: I saw somebody else who seems to have the same problem posted about it in the forums, too. But this was in other, as it seems, unrelated threads. I couldn't find anything else about it, so I'm opening a new one.