Fix strip_tags modifier for falsy input.

Fixes #890

CHANGELOG.md

@@ -8,7 +8,6 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - `|strip_tags` does not work if the input is 0 [#890](https://github.com/smarty-php/smarty/issues/890)
-- Use of negative numbers in {math} equations [#895](https://github.com/smarty-php/smarty/issues/895)
 
 ## [4.3.2] - 2023-07-19
 

libs/plugins/function.math.php

@@ -67,7 +67,7 @@ function smarty_function_math($params, $template)
     $equation = preg_replace('/\s+/', '', $equation);
 
     // Adapted from https://www.php.net/manual/en/function.eval.php#107377
-    $number = '-?(?:\d+(?:[,.]\d+)?|pi|π)'; // What is a number
+    $number = '(?:\d+(?:[,.]\d+)?|pi|π)'; // What is a number
     $functionsOrVars = '((?:0x[a-fA-F0-9]+)|([a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*))';
     $operators = '[,+\/*\^%-]'; // Allowed math operators
     $regexp = '/^(('.$number.'|'.$functionsOrVars.'|('.$functionsOrVars.'\s*\((?1)*\)|\((?1)*\)))(?:'.$operators.'(?1))?)+$/';

libs/sysplugins/smarty_template_compiled.php

@@ -85,7 +85,7 @@ class Smarty_Template_Compiled extends Smarty_Template_Resource_Base
      *
      * @param Smarty_Internal_Template $_template
      *
-     * @return void
+     * @return string
      * @throws Exception
      */
     public function render(Smarty_Internal_Template $_template)

tests/UnitTests/TemplateSource/ValueTests/Math/MathTest.php

@@ -101,14 +101,6 @@ class MathTest extends PHPUnit_Smarty
         $this->assertEquals($expected, $this->smarty->fetch($tpl));
     }
 
-    public function testNegativeNumbers()
-    {
-        $this->smarty->disableSecurity();
-        $expected = "-19 -- 4.1";
-        $tpl = $this->smarty->createTemplate('eval:{$x = 4}{$y = 5.5}{math equation="-2.0*(x+y)" x=$x y=$y} -- {math equation="-20.5 / -5"}');
-        $this->assertEquals($expected, $this->smarty->fetch($tpl));
-    }
-
     public function testSyntaxFormat()
     {
         $this->smarty->disableSecurity();