diff --git a/CHANGELOG.md b/CHANGELOG.md
index d44c1fec..3b9989a8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 - Dropped support for PHP7.0 and below, so Smarty now requires PHP >=7.1
 - Dropped support for php asp tags in templates (removed from php since php7.0)
+- Removed all PHP_VERSION_ID and compare_version checks and conditional code blocks that are now no longer required
 
 ## [3.1.37] - 2021-01-07
 
diff --git a/libs/Autoloader.php b/libs/Autoloader.php
index c09361b6..e909d434 100644
--- a/libs/Autoloader.php
+++ b/libs/Autoloader.php
@@ -76,11 +76,7 @@ class Smarty_Autoloader
         self::$SMARTY_DIR = defined('SMARTY_DIR') ? SMARTY_DIR : dirname(__FILE__) . DIRECTORY_SEPARATOR;
         self::$SMARTY_SYSPLUGINS_DIR = defined('SMARTY_SYSPLUGINS_DIR') ? SMARTY_SYSPLUGINS_DIR :
             self::$SMARTY_DIR . 'sysplugins' . DIRECTORY_SEPARATOR;
-        if (version_compare(PHP_VERSION, '5.3.0', '>=')) {
-            spl_autoload_register(array(__CLASS__, 'autoload'), true, $prepend);
-        } else {
-            spl_autoload_register(array(__CLASS__, 'autoload'));
-        }
+        spl_autoload_register(array(__CLASS__, 'autoload'), true, $prepend);
     }
 
     /**
diff --git a/libs/plugins/modifier.escape.php b/libs/plugins/modifier.escape.php
index 150901c7..35bf9720 100644
--- a/libs/plugins/modifier.escape.php
+++ b/libs/plugins/modifier.escape.php
@@ -23,12 +23,9 @@
  */
 function smarty_modifier_escape($string, $esc_type = 'html', $char_set = null, $double_encode = true)
 {
-    static $_double_encode = null;
+    static $_double_encode = true;
     static $is_loaded_1 = false;
     static $is_loaded_2 = false;
-    if ($_double_encode === null) {
-        $_double_encode = version_compare(PHP_VERSION, '5.2.3', '>=');
-    }
     if (!$char_set) {
         $char_set = Smarty::$_CHARSET;
     }
diff --git a/libs/plugins/modifiercompiler.escape.php b/libs/plugins/modifiercompiler.escape.php
index e0763adc..0eabebf8 100644
--- a/libs/plugins/modifiercompiler.escape.php
+++ b/libs/plugins/modifiercompiler.escape.php
@@ -22,7 +22,7 @@
  */
 function smarty_modifiercompiler_escape($params, Smarty_Internal_TemplateCompilerBase $compiler)
 {
-    static $_double_encode = null;
+    static $_double_encode = true;
     static $is_loaded = false;
     $compiler->template->_checkPlugins(
         array(
@@ -32,9 +32,6 @@ function smarty_modifiercompiler_escape($params, Smarty_Internal_TemplateCompile
             )
         )
     );
-    if ($_double_encode === null) {
-        $_double_encode = version_compare(PHP_VERSION, '5.2.3', '>=');
-    }
     try {
         $esc_type = smarty_literal_compiler_param($params, 1, 'html');
         $char_set = smarty_literal_compiler_param($params, 2, Smarty::$_CHARSET);
diff --git a/libs/plugins/shared.escape_special_chars.php b/libs/plugins/shared.escape_special_chars.php
index 6b18d3ee..a204b092 100644
--- a/libs/plugins/shared.escape_special_chars.php
+++ b/libs/plugins/shared.escape_special_chars.php
@@ -20,13 +20,7 @@
 function smarty_function_escape_special_chars($string)
 {
     if (!is_array($string)) {
-        if (version_compare(PHP_VERSION, '5.2.3', '>=')) {
-            $string = htmlspecialchars($string, ENT_COMPAT, Smarty::$_CHARSET, false);
-        } else {
-            $string = preg_replace('!&(#?\w+);!', '%%%SMARTY_START%%%\\1%%%SMARTY_END%%%', $string);
-            $string = htmlspecialchars($string);
-            $string = str_replace(array('%%%SMARTY_START%%%', '%%%SMARTY_END%%%'), array('&', ';'), $string);
-        }
+        $string = htmlspecialchars($string, ENT_COMPAT, Smarty::$_CHARSET, false);
     }
     return $string;
 }
diff --git a/libs/sysplugins/smarty_internal_cacheresource_file.php b/libs/sysplugins/smarty_internal_cacheresource_file.php
index 61618449..abed98d8 100644
--- a/libs/sysplugins/smarty_internal_cacheresource_file.php
+++ b/libs/sysplugins/smarty_internal_cacheresource_file.php
@@ -196,11 +196,7 @@ class Smarty_Internal_CacheResource_File extends Smarty_CacheResource
      */
     public function hasLock(Smarty $smarty, Smarty_Template_Cached $cached)
     {
-        if (version_compare(PHP_VERSION, '5.3.0', '>=')) {
-            clearstatcache(true, $cached->lock_id);
-        } else {
-            clearstatcache();
-        }
+        clearstatcache(true, $cached->lock_id);
         if (is_file($cached->lock_id)) {
             $t = filemtime($cached->lock_id);
             return $t && (time() - $t < $smarty->locking_timeout);
diff --git a/libs/sysplugins/smarty_internal_templatecompilerbase.php b/libs/sysplugins/smarty_internal_templatecompilerbase.php
index 3cc957de..3f6b1668 100644
--- a/libs/sysplugins/smarty_internal_templatecompilerbase.php
+++ b/libs/sysplugins/smarty_internal_templatecompilerbase.php
@@ -649,12 +649,8 @@ abstract class Smarty_Internal_TemplateCompilerBase
                         $this->trigger_template_error("Illegal number of parameter in '{$func_name()}'");
                     }
                     if ($func_name === 'empty') {
-                        if (!$this->syntaxMatchesVariable($parameter[0]) && version_compare(PHP_VERSION, '5.5.0', '<')) {
-                            return '(' . $parameter[ 0 ] . ' === false )';
-                        } else {
-                            return $func_name . '(' .
-                                   str_replace("')->value", "',null,true,false)->value", $parameter[ 0 ]) . ')';
-                        }
+                        return $func_name . '(' .
+                               str_replace("')->value", "',null,true,false)->value", $parameter[ 0 ]) . ')';
                     } else {
                         return $func_name . '(' . $parameter[ 0 ] . ')';
                     }
diff --git a/tests/UnitTests/ConfigFileTests/file/ConfigVarTest.php b/tests/UnitTests/ConfigFileTests/file/ConfigVarTest.php
index 465b4966..b4f9473d 100644
--- a/tests/UnitTests/ConfigFileTests/file/ConfigVarTest.php
+++ b/tests/UnitTests/ConfigFileTests/file/ConfigVarTest.php
@@ -403,11 +403,7 @@ class ConfigVarTest extends PHPUnit_Smarty
             $this->assertEquals("", $this->smarty->fetch('foo.tpl'));
         }
         catch (Exception $e) {
-	        if (PHP_VERSION_ID >= 80000) {
-		        $this->assertStringStartsWith('Undefined variable', $e->getMessage());
-	        } else {
-		        $this->assertStringStartsWith('Undefined variable', $e->getMessage());
-	        }
+	        $this->assertStringStartsWith('Undefined variable', $e->getMessage());
         }
     }
 }
diff --git a/tests/UnitTests/TemplateSource/TagTests/Php/CompilePhpTest.php b/tests/UnitTests/TemplateSource/TagTests/Php/CompilePhpTest.php
index cfb4f152..d2a49446 100644
--- a/tests/UnitTests/TemplateSource/TagTests/Php/CompilePhpTest.php
+++ b/tests/UnitTests/TemplateSource/TagTests/Php/CompilePhpTest.php
@@ -170,9 +170,6 @@ echo \'bar \';
 $foo = 3;
 { /php}<--', 'PHP_ALLOW, \'phptag_literal.tpl\''),
         );
-        if (version_compare(phpversion(), '5.7.0', '<')) {
-            $data[] = array(Smarty::PHP_ALLOW, 'script.tpl', '<br> This is a script <br> 5<br>', 'PHP_ALLOW, \'script.tpl\'');
-        }
         return $data;
     }
     /*