fix php7.4 deprecation and remove php7.4 from travis allow_failures since php7.4 is current stable

Revert "Reinstitute the phpunit/phpunit dependency the right way."

change_log.txt

@@ -1,6 +1,4 @@
  - fix foreachelse on arrayiterators https://github.com/smarty-php/smarty/issues/506
- - throw SmartyException when setting caching attributes for cacheable plugin https://github.com/smarty-php/smarty/issues/457
- - fix errors that occured where isset was replaced with null check such as https://github.com/smarty-php/smarty/issues/453
 
 ===== 3.1.34 release ===== 05.11.2019
 13.01.2020

libs/sysplugins/smarty_internal_method_registerplugin.php

@@ -48,8 +48,6 @@ class Smarty_Internal_Method_RegisterPlugin
             throw new SmartyException("Plugin tag '{$name}' already registered");
         } elseif (!is_callable($callback)) {
             throw new SmartyException("Plugin '{$name}' not callable");
-        } elseif ($cacheable && $cache_attr) {
-            throw new SmartyException("Cannot set caching attributes for plugin '{$name}' when it is cacheable.");
         } else {
             $smarty->registered_plugins[ $type ][ $name ] = array($callback, (bool)$cacheable, (array)$cache_attr);
         }

libs/sysplugins/smarty_internal_templatecompilerbase.php

@@ -621,18 +621,22 @@ abstract class Smarty_Internal_TemplateCompilerBase
                 || strcasecmp($name, 'array') === 0 || is_callable($name)
             ) {
                 $func_name = strtolower($name);
-
+                $par = implode(',', $parameter);
+                $parHasFuction = strpos($par, '(') !== false;
                 if ($func_name === 'isset') {
                     if (count($parameter) === 0) {
                         $this->trigger_template_error('Illegal number of parameter in "isset()"');
                     }
-
-	                $pa = array();
-	                foreach ($parameter as $p) {
-		                $pa[] = $this->syntaxMatchesVariable($p) ? 'isset(' . $p . ')' : '(' . $p . ' !== null )';
-	                }
-	                return '(' . implode(' && ', $pa) . ')';
-
+                    if ($parHasFuction) {
+                        $pa = array();
+                        foreach ($parameter as $p) {
+                            $pa[] = (strpos($p, '(') === false) ? ('isset(' . $p . ')') : ('(' . $p . ' !== null )');
+                        }
+                        return '(' . implode(' && ', $pa) . ')';
+                    } else {
+                        $isset_par = str_replace("')->value", "',null,true,false)->value", $par);
+                    }
+                    return $name . '(' . $isset_par . ')';
                 } elseif (in_array(
                     $func_name,
                     array(
@@ -649,7 +653,7 @@ abstract class Smarty_Internal_TemplateCompilerBase
                         $this->trigger_template_error("Illegal number of parameter in '{$func_name()}'");
                     }
                     if ($func_name === 'empty') {
-                        if (!$this->syntaxMatchesVariable($parameter[0]) && version_compare(PHP_VERSION, '5.5.0', '<')) {
+                        if ($parHasFuction && version_compare(PHP_VERSION, '5.5.0', '<')) {
                             return '(' . $parameter[ 0 ] . ' === false )';
                         } else {
                             return $func_name . '(' .
@@ -667,18 +671,6 @@ abstract class Smarty_Internal_TemplateCompilerBase
         }
     }
 
-	/**
-	 * Determines whether the passed string represents a valid (PHP) variable.
-	 * This is important, because `isset()` only works on variables and `empty()` can only be passed
-	 * a variable prior to php5.5
-	 * @param $string
-	 * @return bool
-	 */
-	private function syntaxMatchesVariable($string) {
-    	static $regex_pattern = '/^\$[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*((->)[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*|\[.*]*\])*$/';
-    	return 1 === preg_match($regex_pattern, trim($string));
-    }
-
     /**
      * This method is called from parser to process a text content section
      * - remove text from inheritance child templates as they may generate output