GH Actions: set short_open_tag ini setting for PHP 5.3 test run

The tests for this PR were failing after support for PHP 5.3 had been added back.

Reason being that the short PHP open echo tags `<?=` are only recognized as such with the ini setting `short_open_tag` turned on in PHP 5.3.

I would normally add this to the matrix to do a complete test run with and without `short_open_tag`, but as this only affects PHP 5.3, I think that's a little over the top.

Instead this commit adds a tweak to the test workflow to turn that ini setting on for the PHP 5.3 test run.

Ref: https://www.php.net/manual/en/ini.core.php#ini.short-open-tag

.github/workflows/test.yml

@@ -32,11 +32,22 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v2
 
+      - name: Setup ini config
+        id: set_ini
+        run: |
+          # On PHP 5.3, short_open_tag needs to be turned on for short open echo tags to be recognized
+          # a PHP tags. As this only affects PHP 5.3, this is not something of serious concern.
+          if [ ${{ matrix.php }} == "5.3" ]; then
+            echo '::set-output name=PHP_INI::zend.assertions=1, error_reporting=-1, display_errors=On, short_open_tag=On'
+          else
+            echo '::set-output name=PHP_INI::zend.assertions=1, error_reporting=-1, display_errors=On'
+          fi
+
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php }}
-          ini-values: zend.assertions=1, error_reporting=-1, display_errors=On
+          ini-values: ${{ steps.set_ini.outputs.PHP_INI }}
           coverage: none
           tools: cs2pr