Running you exact code gives me the error "Parse error: syntax error, unexpected end of file in /in/VQqm7 on line 12" - https://3v4l.org/VQqm7

That's because there are spaces before the "BAR;" in your script, and the parser gets to the end of the file unexpectedly.

Removing those spaces makes the script work - https://3v4l.org/19bhe 

However I'm going to leave this open as the error has changed for PHP7.3alpha, and it makes no sense.

tl:dr - the error message for unclosed heredoc makes no sense for PHP 7.3alpaha

To:
Parse error: Invalid body indentation level (expecting an indentation level of at least 1) in /in/VQqm7 on line 10

From
Parse error: syntax error, unexpected end of file in /in/VQqm7 on line 12

In PHP 7.3 the doc string *is* terminated. The code as written should be working fine, the indentation error is spurious.

The heredoc should not be considered unclosed in 7.3, since https://wiki.php.net/rfc/flexible_heredoc_nowdoc_syntaxes .

The dot triggers the problem. With removed dot the script works in 7.3alpha1: https://3v4l.org/VeX0p

The problem is that strip_multiline_string_indentation() is called
after *any* variable[1], resulting in the parse error, if the
variable is not followed by whitespace, and resulting in removed
whitespace otherwise.  E.g.

<?php
$foo = 'foo';
echo <<<BAR
 $foo bar
 BAR;

outputs `foobar` instead of the expected `foo bar`.

Thomas, could you please have a look at this issue?

[1] <https://github.com/php/php-src/blob/php-7.3.0alpha1/Zend/zend_language_scanner.l#L2589>
    <https://github.com/php/php-src/blob/php-7.3.0alpha1/Zend/zend_language_scanner.l#L2594>