diff --git a/phpstan.neon.dist b/phpstan.neon.dist
new file mode 100644
index 00000000..533df9d1
--- /dev/null
+++ b/phpstan.neon.dist
@@ -0,0 +1,13 @@
+parameters:
+  level: 1
+  paths:
+    - src
+    - package-command.php
+  scanDirectories:
+    - vendor/wp-cli/wp-cli/php
+  scanFiles:
+    - vendor/php-stubs/wordpress-stubs/wordpress-stubs.php
+  treatPhpDocTypesAsCertain: false
+  ignoreErrors:
+    # WP_CLI_VERSION is defined in wp-cli core at runtime
+    - '#Constant WP_CLI_VERSION not found#'
diff --git a/src/Package_Command.php b/src/Package_Command.php
index 7a3fff80..0d698b7b 100644
--- a/src/Package_Command.php
+++ b/src/Package_Command.php
@@ -737,12 +737,8 @@ private function package_index() {
 
 			$io = new NullIO();
 			try {
-				if ( $this->is_composer_v2() ) {
-					$http_downloader = new HttpDownloader( $io, $config );
-					$package_index   = new ComposerRepository( [ 'url' => self::PACKAGE_INDEX_URL ], $io, $config, $http_downloader );
-				} else {
-					$package_index = new ComposerRepository( [ 'url' => self::PACKAGE_INDEX_URL ], $io, $config );
-				}
+				$http_downloader = new HttpDownloader( $io, $config );
+				$package_index   = new ComposerRepository( [ 'url' => self::PACKAGE_INDEX_URL ], $io, $config, $http_downloader );
 			} catch ( Exception $e ) {
 				WP_CLI::error( $e->getMessage() );
 			}
@@ -759,6 +755,7 @@ private function package_index() {
 	 * @param array
 	 */
 	private function show_packages( $context, $packages, $assoc_args ) {
+		$default_fields = [];
 		if ( 'list' === $context ) {
 			$default_fields = [
 				'name',
@@ -1074,7 +1071,7 @@ private function find_latest_package( PackageInterface $package, Composer $compo
 		$stability        = $composer->getPackage()->getMinimumStability();
 		$flags            = $composer->getPackage()->getStabilityFlags();
 		if ( isset( $flags[ $name ] ) ) {
-			$stability = array_search( $flags[ $name ], BasePackage::$stabilities, true );
+			$stability = array_search( $flags[ $name ], BasePackage::STABILITIES, true );
 		}
 		$best_stability = $stability;
 		if ( $composer->getPackage()->getPreferStable() ) {
diff --git a/src/WP_CLI/JsonManipulator.php b/src/WP_CLI/JsonManipulator.php
index 1a4e6dc7..95df1699 100644
--- a/src/WP_CLI/JsonManipulator.php
+++ b/src/WP_CLI/JsonManipulator.php
@@ -128,7 +128,7 @@ public function addLink($type, $package, $constraint, $sortPackages = false, $ca
     private function sortPackages(array &$packages = array())
     {
         $prefix = function ($requirement) {
-            if (preg_match(PlatformRepository::PLATFORM_PACKAGE_REGEX, $requirement)) {
+            if (PlatformRepository::isPlatformPackage($requirement)) {
                 return preg_replace(
                     array(
                         '/^php/',
@@ -248,7 +248,7 @@ public function addSubNode($mainNode, $name, $value, $caseInsensitive = false) /
         // child exists
         $childRegex = '{'.self::$DEFINES.'(?P<start>"'.preg_quote($name).'"\s*:\s*)(?P<content>(?&json))(?P<end>,?)}x';
         if ($this->pregMatch($childRegex, $children, $matches)) {
-            $children = preg_replace_callback($childRegex, function ($matches) use ($name, $subName, $value, $that) {
+            $children = preg_replace_callback($childRegex, function ($matches) use ($subName, $value, $that) {
                 if ($subName !== null) {
                     $curVal = json_decode($matches['content'], true);
                     if (!is_array($curVal)) {
@@ -362,6 +362,7 @@ public function removeSubNode($mainNode, $name, $caseInsensitive = false) // WP_
         }
 
         // try and find a match for the subkey
+        $childrenClean = $children;
         if ($this->pregMatch('{"'.preg_quote($name).'"\s*:}i', $children)) {
             // find best match for the value of "name"
             if (preg_match_all('{'.self::$DEFINES.'"'.preg_quote($name).'"\s*:\s*(?:(?&json))}x', $children, $matches)) {
@@ -379,8 +380,6 @@ public function removeSubNode($mainNode, $name, $caseInsensitive = false) // WP_
                     }
                 }
             }
-        } else {
-            $childrenClean = $children;
         }
 
         // no child data left, $name was the only key in