Description:
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SQLite allows to open database with empty filename (https://www.sqlite.org/c3ref/open.html):

> If the filename is an empty string, then a private, temporary on-disk database will be created. This private database will be automatically deleted as soon as the database connection is closed.

This is also true for HHVM implementation: https://github.com/facebook/hhvm/issues/7225

Would be nice to be consistent and add support for this in PHP as well (especially, since underlying interface already have it).

P.S. https://bugs.php.net/bug.php?id=27928 doesn't seem to be relevant here anymore

Test script:
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<?php
new SQLite3('');

Expected result:
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No output

Actual result:
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PHP Fatal error:  Uncaught Exception: Unable to expand filepath in %s:2
Stack trace:
#0 %s(2): SQLite3->__construct('')
#1 {main}
  thrown in %s on line 2