PHPStan\Broker\Broker::getFunction PHP Method

    public function getFunction(\PhpParser\Node\Name $nameNode, Scope $scope = null) : \PHPStan\Reflection\FunctionReflection
    {
        $functionName = $this->resolveFunctionName($nameNode, $scope);
        if ($functionName === null) {
            throw new \PHPStan\Broker\FunctionNotFoundException((string) $nameNode);
        }
        $lowerCasedFunctionName = strtolower($functionName);
        if (!isset($this->functionReflections[$lowerCasedFunctionName])) {
            $this->functionReflections[$lowerCasedFunctionName] = $this->functionReflectionFactory->create(new \ReflectionFunction($lowerCasedFunctionName));
        }
        return $this->functionReflections[$lowerCasedFunctionName];
    }

 /**
  * @param \PhpParser\Node\FunctionLike $function
  * @param \PHPStan\Analyser\Scope $scope
  * @param string $parameterMessage
  * @param string $returnMessage
  * @return string[]
  */
 public function checkFunction(FunctionLike $function, Scope $scope, string $parameterMessage, string $returnMessage) : array
 {
     if ($function instanceof ClassMethod && $scope->getClass() !== null) {
         return $this->checkParametersAcceptor($this->broker->getClass($scope->getClass())->getMethod($function->name), $parameterMessage, $returnMessage);
     }
     if ($function instanceof Function_) {
         $functionName = $function->name;
         if (isset($function->namespacedName)) {
             $functionName = $function->namespacedName;
         }
         return $this->checkParametersAcceptor($this->broker->getFunction(new Name($functionName)), $parameterMessage, $returnMessage);
     }
     $errors = [];
     foreach ($function->getParams() as $param) {
         $class = (string) $param->type;
         if ($class && !in_array($class, self::VALID_TYPEHINTS, true) && !$this->broker->hasClass($class)) {
             $errors[] = sprintf($parameterMessage, $param->name, $class);
         }
     }
     $returnType = (string) $function->getReturnType();
     if ($returnType && !in_array($returnType, self::VALID_TYPEHINTS, true) && !$this->broker->hasClass($returnType)) {
         $errors[] = sprintf($returnMessage, $returnType);
     }
     return $errors;
 }