[MapScript-PHP] initialization of scale only happens on setExtent

[pspencer@…]

Contrary to the documentation for 4.4, the map scale is not calculated by
calling $oMap->prepareQuery().

I also tried $oMap->prepareImage();

It is calculated if you set the extent using 

$oMap->setExtent( $oMap->extent->minx, $oMap->extent->miny, $oMap->extent->maxx,
$oMap->extent->maxy);

need to determine why prepareQuery/prepareImage are not calculating scale or
update documentation to reflect use of setExtent as only valid way to calculate
extent.

[assefa]

prepareQuery now updated the scale.