Hmm, this is strange. This error looks like a PHP error, but the installer
(based on InnoSetup) doesn't use PHP. Once installation is complete, the
installer launches phpgui.exe which of course uses PHP, perhaps this is
the point where you saw this error.
However I'm sure it doesn't need and use the
xmlXPatthCompiledEvalToBoolean function, neither I am sure what LIBPQ.dll
is. Perhaps it somehow interferes with another php.ini. Do you have other
installations of PHP on your computer? PHP GUI may use its php.ini and
then you see these errors.
However PHPExe uses its own php.ini and should be OK in situations like
this.