Increase minimum php version requirements

[colemanw]

Overview

As promised in our blog post we are incrementing the minimum php requirements for CiviCRM.

Issue is here: https://lab.civicrm.org/infrastructure/ops/issues/818

Before/After

	Before	After
Min to run	5.3	5.4
Min to install	5.3	5.4*
Min recommended ver	5.5	5.6
Recommended ver	5.6	7.0

* We'll bump this to 5.5 in the following release as promised.

[colemanw]

@totten this refactors a function in the install script so you'll want to merge this before tackling that rewrite.

[totten]

jenkins, test this please

[totten]

jenkins, test this please

[totten]

jenkins, test this please

[colemanw]

@civicrm-builder test this please

[totten]

@colemanw I pushed up a couple small tweaks.

I was r-running it, and the install screen worked well. For the upgrade screen, I did this hack to simulate an old version:

diff --git a/CRM/Upgrade/Incremental/General.php b/CRM/Upgrade/Incremental/General.php
index 56a80610d2..c97acf55ef 100644
--- a/CRM/Upgrade/Incremental/General.php
+++ b/CRM/Upgrade/Incremental/General.php
@@ -65,7 +65,7 @@ class CRM_Upgrade_Incremental_General {
    */
   public static function setPreUpgradeMessage(&$preUpgradeMessage, $currentVer, $latestVer) {
     $dateFormat = Civi::Settings()->get('dateformatshortdate');
-    if (version_compare(phpversion(), self::MIN_RECOMMENDED_PHP_VER) < 0) {
+    if (version_compare('5.3.20', self::MIN_RECOMMENDED_PHP_VER) < 0) {
       $preUpgradeMessage .= '<p>';
       $preUpgradeMessage .= ts('You may proceed with the upgrade and CiviCRM %1 will continue working normally, but future releases will require PHP %2 or above. We recommend PHP version %3.', array(
          1 => $latestVer,

and the resulting message was this, which seems to suggest that you could continue with an upgrade on PHP 5.3:

[colemanw]

Hmm, @totten a fatal error ought to be triggered before we get to that screen, oughtn't it? Perhaps because you only changed the variable in one place that didn't happen.
Looks like \CRM_Upgrade_Form::checkUpgradeableVersion() should stop us from getting to that screen.

[totten]

Thanks, @colemanw. Makes sense now. 👍

[colemanw]

@totten based on discussion on dev-post-release I've cherry-picked this into the 4.7.29-rc branch.