Bugfix/rand without param v3 (#796)

* Fixed use of `rand()` without a parameter in math function (for v3.1)
Fixes #794

* Add change in regex for PRCE (PHP < 7.3)

* Add unit tests and correctly set PHP supported versions

* Drop PHP5.2 from CI workflows because it cannot be build anymore

* Fix CI workflow for PHP7.2 and up

* re-add compose packages cache with specific key

* Exclude unit test files from git export

* prevent double CI workflows in PRs

utilities/testrunners/shared/install-composer.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+EXPECTED_CHECKSUM="$(php -r 'copy("https://composer.github.io/installer.sig", "php://stdout");')"
+php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
+ACTUAL_CHECKSUM="$(php -r "echo hash_file('sha384', 'composer-setup.php');")"
+
+if [ "$EXPECTED_CHECKSUM" != "$ACTUAL_CHECKSUM" ]
+then
+    >&2 echo 'ERROR: Invalid installer checksum'
+    rm composer-setup.php
+    exit 1
+fi
+
+php composer-setup.php --quiet
+RESULT=$?
+rm composer-setup.php
+exit $RESULT