php-eval: unexpected '=' in drush/commands/core/core.drush.inc(658)

For those who find this via Search engines, you can pipe to `drush php-eval` like follows, depending on what style you like in bash.

read -r -d '' DRUSH_TEMP_COMMAND <<'EOF'; ./vendor/bin/drush php-eval "$DRUSH_TEMP_COMMAND"
var_dump(\Drupal::service('file_system')->getTempDirectory());
var_dump("TEST2");
EOF

OR

DRUSH_TEMP_COMMAND=$(cat <<'END'
var_dump(\Drupal::service('file_system')->getTempDirectory());
var_dump("TEST");
END
); ./vendor/bin/drush php-eval "$DRUSH_TEMP_COMMAND"

@see https://stackoverflow.com/questions/2500436/how-does-cat-eof-work-in-bas...
@see https://stackoverflow.com/questions/1167746/how-to-assign-a-heredoc-valu...