Take set_extension_version function from matrix testing env

Author: alcaeus

.evergreen/run-tests.sh

@@ -17,19 +17,7 @@ PHP_IS_MATRIX_TESTING=${PHP_IS_MATRIX_TESTING:-false}
 
 # For matrix testing, we have to determine the correct driver version
 if [ "$PHP_IS_MATRIX_TESTING" == "true" ]; then
-   set_extension_version () {
-      case $1 in
-         '4.4')
-             export DRIVER_VERSION='1.8.2'
-             ;;
-         '4.2')
-            export DRIVER_VERSION='1.6.1'
-            ;;
-         '4.0')
-            export DRIVER_VERSION='1.5.5'
-            ;;
-      esac
-   }
+   eval "$PHP_SET_EXTENSION_VERSION"
 
    set_extension_version "${DRIVER_MONGODB_VERSION}"