Bump Minimum Required PHP to be 5.6

[seamuslee001]

Overview

This bumps the minimum required PHP version to be 5.6 as per https://civicrm.org/blog/eileen/end-of-life-plans-for-5x-php-versions-planning-for-70-eol

Before

Previously minimum php version was 5.5

After

Minimum php version is 5.6

ping @totten @eileenmcnaughton

[civibot]

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[eileenmcnaughton]

@seamuslee001 we should do this for sure. I think we should possibly also increase the const MIN_RECOMMENDED_PHP_VER = '7.0'; variable - since this is the last month of php support for it

[seamuslee001]

@eileenmcnaughton are we prepared to recommend anything higher than 7.1 at this stage?

[eileenmcnaughton]

And in fact const RECOMMENDED_PHP_VER = '7.1'; - we should be recommending php 7.2 now IMHO

[eileenmcnaughton]

ah snap - YES I think so - there is the smtp password version but I think we just live with the advice that people re-save their passwords when updating to php 7.2

[seamuslee001]

done that now @eileenmcnaughton

[eileenmcnaughton]

OK - looks good to me!

[seamuslee001]

Jenkins re test this please

[eileenmcnaughton]

@seamuslee001 this is the wrong branch I just realised - 5.9 will be the last php 5.5 supporting version

[seamuslee001]

@eileenmcnaughton switched to master

[seamuslee001]

Merging as per tag