GraphQL\Executor\Values::getVariableValues PHP Method

    public static function getVariableValues(Schema $schema, $definitionNodes, array $inputs)
    {
        $coercedValues = [];
        foreach ($definitionNodes as $definitionNode) {
            $varName = $definitionNode->variable->name->value;
            $varType = Utils\TypeInfo::typeFromAST($schema, $definitionNode->type);
            if (!Type::isInputType($varType)) {
                throw new Error('Variable "$' . $varName . '" expected value of type ' . '"' . Printer::doPrint($definitionNode->type) . '" which cannot be used as an input type.', [$definitionNode->type]);
            }
            if (!array_key_exists($varName, $inputs)) {
                $defaultValue = $definitionNode->defaultValue;
                if ($defaultValue) {
                    $coercedValues[$varName] = Utils\AST::valueFromAST($defaultValue, $varType);
                }
                if ($varType instanceof NonNull) {
                    throw new Error('Variable "$' . $varName . '" of required type ' . '"' . Utils::printSafe($varType) . '" was not provided.', [$definitionNode]);
                }
            } else {
                $value = $inputs[$varName];
                $errors = self::isValidPHPValue($value, $varType);
                if (!empty($errors)) {
                    $message = "\n" . implode("\n", $errors);
                    throw new Error('Variable "$' . $varName . '" got invalid value ' . json_encode($value) . '.' . $message, [$definitionNode]);
                }
                $coercedValue = self::coerceValue($varType, $value);
                Utils::invariant($coercedValue !== Utils::undefined(), 'Should have reported error.');
                $coercedValues[$varName] = $coercedValue;
            }
        }
        return $coercedValues;
    }

 /**
  * Constructs a ExecutionContext object from the arguments passed to
  * execute, which we will pass throughout the other execution methods.
  *
  * @param Schema $schema
  * @param DocumentNode $documentNode
  * @param $rootValue
  * @param $contextValue
  * @param $rawVariableValues
  * @param string $operationName
  * @return ExecutionContext
  * @throws Error
  */
 private static function buildExecutionContext(Schema $schema, DocumentNode $documentNode, $rootValue, $contextValue, $rawVariableValues, $operationName = null)
 {
     $errors = [];
     $fragments = [];
     $operation = null;
     foreach ($documentNode->definitions as $definition) {
         switch ($definition->kind) {
             case NodeKind::OPERATION_DEFINITION:
                 if (!$operationName && $operation) {
                     throw new Error('Must provide operation name if query contains multiple operations.');
                 }
                 if (!$operationName || isset($definition->name) && $definition->name->value === $operationName) {
                     $operation = $definition;
                 }
                 break;
             case NodeKind::FRAGMENT_DEFINITION:
                 $fragments[$definition->name->value] = $definition;
                 break;
             default:
                 throw new Error("GraphQL cannot execute a request containing a {$definition->kind}.", [$definition]);
         }
     }
     if (!$operation) {
         if ($operationName) {
             throw new Error("Unknown operation named \"{$operationName}\".");
         } else {
             throw new Error('Must provide an operation.');
         }
     }
     $variableValues = Values::getVariableValues($schema, $operation->variableDefinitions ?: [], $rawVariableValues ?: []);
     $exeContext = new ExecutionContext($schema, $fragments, $rootValue, $contextValue, $operation, $variableValues, $errors);
     return $exeContext;
 }