Show deprecation notice when phpStyleBooleans is not defined and a boolean is encountered.

Co-Authored-By: Will Rowe <willrowe@users.noreply.github.com>

Author: antoineveldhoven

src/twig.core.js

@@ -698,15 +698,17 @@ module.exports = function (Twig) {
         const {phpStyleBooleans} = this.options;
 
         // Conform Javascript boolean to PHP boolean
-        if (phpStyleBooleans) {
-            output = output.map(str => {
-                if (typeof str === 'boolean') {
+        output = output.map(str => {
+            if (typeof str === 'boolean') {
+                if (phpStyleBooleans === undefined) {
+                    console.warn('Deprecation notice: `phpStyleBooleans` is not defined, output differs from PHP behavior, in future versions this behavior will be changed to PHP style booleans.');
+                } else if (phpStyleBooleans) {
                     str = str ? '1' : '';
                 }
+            }
 
-                return str;
-            });
-        }
+            return str;
+        });
 
         if (!autoescape) {
             return output.join('');

src/twig.exports.js

@@ -23,7 +23,8 @@ module.exports = function (Twig) {
             // TODO: turn autoscape on in the next major version
             autoescape: (params.autoescape !== null && params.autoescape) || false,
             allowInlineIncludes: params.allowInlineIncludes || false,
-            phpStyleBooleans: params.phpStyleBooleans || false,
+            // TODO: turn phpStyleBooleans on in the next major version
+            phpStyleBooleans: undefined,
             rethrow: params.rethrow || false,
             namespaces: params.namespaces
         };
@@ -40,6 +41,10 @@ module.exports = function (Twig) {
             Twig.trace = params.trace;
         }
 
+        if (params.phpStyleBooleans !== undefined) {
+            options.phpStyleBooleans = params.phpStyleBooleans;
+        }
+
         if (params.data !== undefined) {
             return Twig.Templates.parsers.twig({
                 data: params.data,