Plesk Migrator is inaccessible on Plesk Onyx: unexpected ‘array’ (T_ARRAY), expecting variable (T_VARIABLE)

Symptoms

• The Plesk Migrator extension fails to open with an error:

  ERROR: syntax error, unexpected 'array' (T_ARRAY), expecting variable (T_VARIABLE) (SessionDirectory.php:13)

• Plesk Migrator was update to a recent version

• The server is running Plesk Onyx or old Obsidian (e.g. 18.0.34)

Cause

Recent Plesk Migrator versions are not compatible with Plesk Onyx.

Resolution

The migrator extension should be installed on the target server. It is not needed on the source server. Any migrations should be carried out to a modern, supported system.