From a3cbdc46fbee148f2e0a7c2bf8f0840e5ef2dce0 Mon Sep 17 00:00:00 2001
From: Simon Wisselink <wisskid@users.noreply.github.com>
Date: Fri, 4 Aug 2023 22:40:19 +0200
Subject: [PATCH] Fix strip_tags modifier for falsy input. (#893)

Fixes #890
---
 CHANGELOG.md                                  |  3 ++
 libs/plugins/modifiercompiler.strip_tags.php  |  2 +-
 .../PluginModifierStripTagsTest.php           | 46 +++++++++++++++++++
 3 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 tests/UnitTests/TemplateSource/TagTests/PluginModifier/PluginModifierStripTagsTest.php

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 10c66c77..20c5b00e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- `|strip_tags` does not work if the input is 0 [#890](https://github.com/smarty-php/smarty/issues/890)
+
 ## [4.3.2] - 2023-07-19
 
 ### Fixed
diff --git a/libs/plugins/modifiercompiler.strip_tags.php b/libs/plugins/modifiercompiler.strip_tags.php
index bd866a61..fd6cc725 100644
--- a/libs/plugins/modifiercompiler.strip_tags.php
+++ b/libs/plugins/modifiercompiler.strip_tags.php
@@ -21,7 +21,7 @@
 function smarty_modifiercompiler_strip_tags($params)
 {
     if (!isset($params[ 1 ]) || $params[ 1 ] === true || trim($params[ 1 ], '"') === 'true') {
-        return "preg_replace('!<[^>]*?>!', ' ', {$params[0]} ?: '')";
+        return "preg_replace('!<[^>]*?>!', ' ', (string) {$params[0]})";
     } else {
         return 'strip_tags((string) ' . $params[ 0 ] . ')';
     }
diff --git a/tests/UnitTests/TemplateSource/TagTests/PluginModifier/PluginModifierStripTagsTest.php b/tests/UnitTests/TemplateSource/TagTests/PluginModifier/PluginModifierStripTagsTest.php
new file mode 100644
index 00000000..c0860a27
--- /dev/null
+++ b/tests/UnitTests/TemplateSource/TagTests/PluginModifier/PluginModifierStripTagsTest.php
@@ -0,0 +1,46 @@
+<?php
+/**
+ * Smarty PHPunit tests of modifier
+ */
+
+namespace UnitTests\TemplateSource\TagTests\PluginModifier;
+use PHPUnit_Smarty;
+
+/**
+ * class for modifier tests
+ *
+ * @runTestsInSeparateProcess
+ * @preserveGlobalState disabled
+ * @backupStaticAttributes enabled
+ */
+class PluginModifierStripTagsTest extends PHPUnit_Smarty {
+
+	public function setUp(): void {
+		$this->setUpSmarty(__DIR__);
+	}
+
+	public function testDefault() {
+		$tpl = $this->smarty->createTemplate('string:{$x|strip_tags}');
+		$tpl->assign('x', '<b>hi</b>');
+		$this->assertEquals(" hi ", $this->smarty->fetch($tpl));
+	}
+
+	public function testParam1() {
+		$tpl = $this->smarty->createTemplate('string:{$x|strip_tags:false}');
+		$tpl->assign('x', '<b>hi</b>');
+		$this->assertEquals("hi", $this->smarty->fetch($tpl));
+	}
+
+	public function testInputIsFalsy0() {
+		$tpl = $this->smarty->createTemplate('string:{$x|strip_tags}');
+		$tpl->assign('x', 0);
+		$this->assertEquals("0", $this->smarty->fetch($tpl));
+	}
+
+	public function testInputIsFalsy1() {
+		$tpl = $this->smarty->createTemplate('string:{$x|strip_tags}');
+		$tpl->assign('x', '');
+		$this->assertEquals("", $this->smarty->fetch($tpl));
+	}
+
+}