Use null coalescing operator

.github/phpstan-baseline.neon

@@ -3215,11 +3215,6 @@ parameters:
 			count: 1
 			path: ../app/code/core/Mage/Sales/Model/Order/Api.php
 
-		-
-			message: "#^Variable \\$data in isset\\(\\) always exists and is not nullable\\.$#"
-			count: 1
-			path: ../app/code/core/Mage/Sales/Model/Order/Creditmemo/Api.php
-
 		-
 			message: "#^Cannot call method addAttributeToFilter\\(\\) on Mage_Core_Model_Resource_Db_Collection_Abstract\\|false\\.$#"
 			count: 1

app/code/core/Mage/Admin/Model/Config.php

@@ -129,11 +129,7 @@ public function getAclAssert($name = '')
             return $asserts;
         }
 
-        if (isset($asserts->$name)) {
-            return $asserts->$name;
-        }
-
-        return false;
+        return $asserts->$name ?? false;
     }
 
     /**
@@ -149,11 +145,7 @@ public function getAclPrivilegeSet($name = '')
             return $sets;
         }
 
-        if (isset($sets->$name)) {
-            return $sets->$name;
-        }
-
-        return false;
+        return $sets->$name ?? false;
     }
 
     /**

app/code/core/Mage/Admin/Model/Observer.php

@@ -64,8 +64,8 @@ public function actionPreDispatchAdmin($observer)
 
                     if ($coreSession->validateFormKey($request->getPost("form_key"))) {
                         $postLogin = $request->getPost('login');
-                        $username = isset($postLogin['username']) ? $postLogin['username'] : '';
-                        $password = isset($postLogin['password']) ? $postLogin['password'] : '';
+                        $username = $postLogin['username'] ?? '';
+                        $password = $postLogin['password'] ?? '';
                         $session->login($username, $password, $request);
                         $request->setPost('login', null);
                     } else {

app/code/core/Mage/Admin/Model/Session.php

@@ -189,7 +189,7 @@ public function login($username, $password, $request = null)
             $this->_loginFailed($e, $request, $username, $message);
         }
 
-        return isset($user) ? $user : null;
+        return $user ?? null;
     }
 
     /**

app/code/core/Mage/AdminNotification/Helper/Data.php

@@ -65,7 +65,7 @@ public function getUnreadNoticeCount($severity)
         if (is_null($this->_unreadNoticeCounts)) {
             $this->_unreadNoticeCounts = Mage::getModel('adminnotification/inbox')->getNoticeStatus();
         }
-        return isset($this->_unreadNoticeCounts[$severity]) ? $this->_unreadNoticeCounts[$severity] : 0;
+        return $this->_unreadNoticeCounts[$severity] ?? 0;
     }
 
     /**

app/code/core/Mage/AdminNotification/Model/Inbox.php

@@ -71,10 +71,7 @@ public function getSeverities($severity = null)
         ];
 
         if (!is_null($severity)) {
-            if (isset($severities[$severity])) {
-                return $severities[$severity];
-            }
-            return null;
+            return $severities[$severity] ?? null;
         }
 
         return $severities;

app/code/core/Mage/Adminhtml/Block/Api/Tab/Rolesedit.php

@@ -64,7 +64,7 @@ public function getResTreeJson()
 
         $rootArray = $this->_getNodeJson($resources,1);
 
-        return Mage::helper('core')->jsonEncode(isset($rootArray['children']) ? $rootArray['children'] : []);
+        return Mage::helper('core')->jsonEncode($rootArray['children'] ?? []);
     }
 
     protected function _sortTree($a, $b)

app/code/core/Mage/Adminhtml/Block/Catalog/Category/Tree.php

@@ -162,13 +162,13 @@ public function getMoveUrl()
     public function getTree($parenNodeCategory=null)
     {
            $rootArray = $this->_getNodeJson($this->getRoot($parenNodeCategory));
-        return isset($rootArray['children']) ? $rootArray['children'] : [];
+        return $rootArray['children'] ?? [];
     }
 
     public function getTreeJson($parenNodeCategory=null)
     {
         $rootArray = $this->_getNodeJson($this->getRoot($parenNodeCategory));
-        return Mage::helper('core')->jsonEncode(isset($rootArray['children']) ? $rootArray['children'] : []);
+        return Mage::helper('core')->jsonEncode($rootArray['children'] ?? []);
     }
 
     /**

app/code/core/Mage/Adminhtml/Block/Catalog/Form/Renderer/Config/DateFieldsOrder.php

@@ -46,9 +46,9 @@ protected function _getElementHtml(Varien_Data_Form_Element_Abstract $element)
         }
 
         $_parts = [];
-        $_parts[] = $element->setValue(isset($values[0]) ? $values[0] : null)->getElementHtml();
-        $_parts[] = $element->setValue(isset($values[1]) ? $values[1] : null)->getElementHtml();
-        $_parts[] = $element->setValue(isset($values[2]) ? $values[2] : null)->getElementHtml();
+        $_parts[] = $element->setValue($values[0] ?? null)->getElementHtml();
+        $_parts[] = $element->setValue($values[1] ?? null)->getElementHtml();
+        $_parts[] = $element->setValue($values[2] ?? null)->getElementHtml();
 
         return implode(' <span>/</span> ', $_parts);
     }

app/code/core/Mage/Adminhtml/Block/Catalog/Form/Renderer/Config/YearRange.php

@@ -38,8 +38,8 @@ protected function _getElementHtml(Varien_Data_Form_Element_Abstract $element)
             $values = [];
         }
 
-        $from = $element->setValue(isset($values[0]) ? $values[0] : null)->getElementHtml();
-        $to = $element->setValue(isset($values[1]) ? $values[1] : null)->getElementHtml();
+        $from = $element->setValue($values[0] ?? null)->getElementHtml();
+        $to = $element->setValue($values[1] ?? null)->getElementHtml();
         return Mage::helper('adminhtml')->__('from') . ' ' . $from
             . ' '
             . Mage::helper('adminhtml')->__('to') . ' ' . $to;

app/code/core/Mage/Adminhtml/Block/Catalog/Product/Edit/Tab/Price/Group/Abstract.php

@@ -150,7 +150,7 @@ public function getCustomerGroups($groupId = null)
         }
 
         if ($groupId !== null) {
-            return isset($this->_customerGroups[$groupId]) ? $this->_customerGroups[$groupId] : [];
+            return $this->_customerGroups[$groupId] ?? [];
         }
 
         return $this->_customerGroups;

app/code/core/Mage/Adminhtml/Block/Customer/Edit/Tab/Newsletter/Grid/Renderer/Status.php

@@ -48,10 +48,6 @@ public function render(Varien_Object $row)
 
     public static function  getStatus($status)
     {
-        if(isset(self::$_statuses[$status])) {
-            return self::$_statuses[$status];
-        }
-
-        return Mage::helper('customer')->__('Unknown');
+        return self::$_statuses[$status] ?? Mage::helper('customer')->__('Unknown');
     }
 }

app/code/core/Mage/Adminhtml/Block/Customer/Edit/Tab/View/Grid/Renderer/Item.php

@@ -62,13 +62,7 @@ protected function _getProductHelper($product)
 
         // Check whether we have helper for our product
         $productType = $product->getTypeId();
-        if (isset($productHelpers[$productType])) {
-            $helperName = $productHelpers[$productType];
-        } else if (isset($productHelpers['default'])) {
-            $helperName = $productHelpers['default'];
-        } else {
-            $helperName = 'catalog/product_configuration';
-        }
+        $helperName = $productHelpers[$productType] ?? $productHelpers['default'] ?? 'catalog/product_configuration';
 
         $helper = Mage::helper($helperName);
         if (!($helper instanceof Mage_Catalog_Helper_Product_Configuration_Interface)) {

app/code/core/Mage/Adminhtml/Block/Customer/Edit/Tab/View/Sales.php

@@ -93,7 +93,7 @@ public function _beforeToHtml()
 
     public function getWebsiteCount($websiteId)
     {
-        return isset($this->_websiteCounts[$websiteId]) ? $this->_websiteCounts[$websiteId] : 0;
+        return $this->_websiteCounts[$websiteId] ?? 0;
     }
 
     public function getRows()

app/code/core/Mage/Adminhtml/Block/Permissions/Tab/Rolesedit.php

@@ -146,7 +146,7 @@ public function getResTreeJson()
 
         $rootArray = $this->_getNodeJson($resources->admin, 1);
 
-        return Mage::helper('core')->jsonEncode(isset($rootArray['children']) ? $rootArray['children'] : []);
+        return Mage::helper('core')->jsonEncode($rootArray['children'] ?? []);
     }
 
     /**

app/code/core/Mage/Adminhtml/Block/Promo/Widget/Chooser/Daterange.php

@@ -119,10 +119,8 @@ public function setRangeValues($from, $to)
     public function setRangeValue($delimitedString)
     {
         $split = explode($this->_rangeDelimiter, $delimitedString, 2);
-        $from = $split[0]; $to = '';
-        if (isset($split[1])) {
-            $to = $split[1];
-        }
+        $from = $split[0];
+        $to = $split[1] ?? '';
         return $this->setRangeValues($from, $to);
     }
 

app/code/core/Mage/Adminhtml/Block/Report/Config/Form/Field/YtdStart.php

@@ -51,12 +51,12 @@ protected function _getElementHtml(Varien_Data_Form_Element_Abstract $element)
 
         $_monthsHtml = $element->setStyle('width:100px;')
             ->setValues($_months)
-            ->setValue(isset($values[0]) ? $values[0] : null)
+            ->setValue($values[0] ?? null)
             ->getElementHtml();
 
         $_daysHtml = $element->setStyle('width:50px;')
             ->setValues($_days)
-            ->setValue(isset($values[1]) ? $values[1] : null)
+            ->setValue($values[1] ?? null)
             ->getElementHtml();
 
         return sprintf('%s %s', $_monthsHtml, $_daysHtml);

app/code/core/Mage/Adminhtml/Block/Sales/Order/Status/New/Form.php

@@ -99,7 +99,7 @@ protected function _prepareForm()
                         'name'      => 'store_labels['.$store->getId().']',
                         'required'  => false,
                         'label'     => $store->getName(),
-                        'value'     => isset($labels[$store->getId()]) ? $labels[$store->getId()] : '',
+                        'value'     => $labels[$store->getId()] ?? '',
                         'fieldset_html_class' => 'store',
                     ]);
                 }

app/code/core/Mage/Adminhtml/Block/System/Config/Form/Field/Array/Abstract.php

@@ -172,7 +172,7 @@ protected function _renderCellTemplate($columnName)
 
         return '<input type="text" name="' . $inputName . '" value="#{' . $columnName . '}" ' .
             ($column['size'] ? 'size="' . $column['size'] . '"' : '') . ' class="' .
-            (isset($column['class']) ? $column['class'] : 'input-text') . '"'.
+            ($column['class'] ?? 'input-text') . '"'.
             (isset($column['style']) ? ' style="'.$column['style'] . '"' : '') . '/>';
     }
 

app/code/core/Mage/Adminhtml/Block/System/Config/Form/Fieldset.php

@@ -199,9 +199,6 @@ protected function _getCollapseState($element)
             return 1;
         }
         $extra = Mage::getSingleton('admin/session')->getUser()->getExtra();
-        if (isset($extra['configState'][$element->getId()])) {
-            return $extra['configState'][$element->getId()];
-        }
-        return false;
+        return $extra['configState'][$element->getId()] ?? false;
     }
 }

app/code/core/Mage/Adminhtml/Block/System/Config/Form/Fieldset/Order/Statuses.php

@@ -64,18 +64,18 @@ protected function _getFieldHtml($fieldset, $id, $status)
     {
         $configData = $this->getConfigData();
         $path = 'sales/order_statuses/status_'.$id; //TODO: move as property of form
-        $data = isset($configData[$path]) ? $configData[$path] : [];
+        $data = $configData[$path] ?? [];
 
         $e = $this->_getDummyElement();
 
         $field = $fieldset->addField($id, 'text',
             [
                 'name'          => 'groups[order_statuses][fields][status_'.$id.'][value]',
                 'label'         => $status,
-                'value'         => isset($data['value']) ? $data['value'] : $status,
-                'default_value' => isset($data['default_value']) ? $data['default_value'] : '',
-                'old_value'     => isset($data['old_value']) ? $data['old_value'] : '',
-                'inherit'       => isset($data['inherit']) ? $data['inherit'] : '',
+                'value'         => $data['value'] ?? $status,
+                'default_value' => $data['default_value'] ?? '',
+                'old_value'     => $data['old_value'] ?? '',
+                'inherit'       => $data['inherit'] ?? '',
                 'can_use_default_value' => $this->getForm()->canUseDefaultValue($e),
                 'can_use_website_value' => $this->getForm()->canUseWebsiteValue($e),
             ])->setRenderer($this->_getFieldRenderer());

app/code/core/Mage/Adminhtml/Block/System/Config/Tabs.php

@@ -153,11 +153,7 @@ public function addTab($code, $config)
      */
     public function getTab($code)
     {
-        if(isset($this->_tabs[$code])) {
-            return $this->_tabs[$code];
-        }
-
-        return null;
+        return $this->_tabs[$code] ?? null;
     }
 
     /**

app/code/core/Mage/Adminhtml/Block/System/Email/Template/Grid/Renderer/Type.php

@@ -34,13 +34,7 @@ class Mage_Adminhtml_Block_System_Email_Template_Grid_Renderer_Type
     ];
     public function render(Varien_Object $row)
     {
-
-        $str = Mage::helper('adminhtml')->__('Unknown');
-
-        if(isset(self::$_types[$row->getTemplateType()])) {
-            $str = self::$_types[$row->getTemplateType()];
-        }
-
+        $str = self::$_types[$row->getTemplateType()] ?? Mage::helper('adminhtml')->__('Unknown');
         return Mage::helper('adminhtml')->__($str);
     }
 }

app/code/core/Mage/Adminhtml/Block/Widget/Grid/Massaction/Abstract.php

@@ -84,11 +84,7 @@ public function addItem($itemId, array $item)
      */
     public function getItem($itemId)
     {
-        if(isset($this->_items[$itemId])) {
-            return $this->_items[$itemId];
-        }
-
-        return null;
+        return $this->_items[$itemId] ?? null;
     }
 
     /**

app/code/core/Mage/Adminhtml/Helper/Dashboard/Abstract.php

@@ -97,15 +97,11 @@ public function setParams(array $params)
 
     public function getParam($name)
     {
-        if(isset($this->_params[$name])) {
-            return $this->_params[$name];
-        }
-
-        return null;
+        return $this->_params[$name] ?? null;
     }
 
     public function getParams()
     {
         return $this->_params;
     }
- }
+}

app/code/core/Mage/Adminhtml/Model/Giftmessage/Save.php

@@ -324,11 +324,7 @@ protected function _getMappedType($type)
             'order_item'    =>  'order_item'
         ];
 
-        if (isset($map[$type])) {
-            return $map[$type];
-        }
-
-        return null;
+        return $map[$type] ?? null;
     }
 
     /**

app/code/core/Mage/Adminhtml/Model/Sales/Order/Random.php

@@ -107,7 +107,7 @@ protected function _getRandomProduct()
     {
         $items = $this->_getProducts();
         $randKey = array_rand($items);
-        return isset($items[$randKey]) ? $items[$randKey] : false;
+        return $items[$randKey] ?? false;
     }
 
     protected function _getStore()

app/code/core/Mage/Adminhtml/Model/System/Config/Backend/Customer/Show/Customer.php

@@ -66,11 +66,7 @@ protected function _afterSave()
         ];
 
         $value = $this->getValue();
-        if (isset($valueConfig[$value])) {
-            $data = $valueConfig[$value];
-        } else {
-            $data = $valueConfig[''];
-        }
+        $data = $valueConfig[$value] ?? $valueConfig[''];
 
         if ($this->getScope() == 'websites') {
             $website = Mage::app()->getWebsite($this->getWebsiteCode());

app/code/core/Mage/Adminhtml/Model/System/Config/Source/Security/Domainpolicy.php

@@ -35,7 +35,7 @@ class Mage_Adminhtml_Model_System_Config_Source_Security_Domainpolicy
      */
     public function __construct($options = [])
     {
-        $this->_helper = isset($options['helper']) ? $options['helper'] : Mage::helper('adminhtml');
+        $this->_helper = $options['helper'] ?? Mage::helper('adminhtml');
     }
 
     /**

app/code/core/Mage/Adminhtml/Model/System/Store.php

@@ -368,10 +368,7 @@ public function getStoreName($storeId)
      **/
     public function getStoreData($storeId)
     {
-        if (isset($this->_storeCollection[$storeId])) {
-            return $this->_storeCollection[$storeId];
-        }
-        return null;
+        return $this->_storeCollection[$storeId] ?? null;
     }
 
     /**

app/code/core/Mage/Adminhtml/controllers/CustomerController.php

@@ -226,11 +226,7 @@ public function saveAction()
                 && Mage::helper('customer')->getIsRequireAdminUserToChangeUserPassword()
             ) {
                 //Validate current admin password
-                if (isset($data['account']['current_password'])) {
-                    $currentPassword = $data['account']['current_password'];
-                } else {
-                    $currentPassword = null;
-                }
+                $currentPassword = $data['account']['current_password'] ?? null;
                 unset($data['account']['current_password']);
                 $errors = $this->_validateCurrentPassword($currentPassword);
             }