framework/validators/UrlValidator.php
public function validateAttribute($model, $attribute)
    {
        $value = $model->$attribute;
        $result = $this->validateValue($value);
        if (!empty($result)) {
            $this->addError($model, $attribute, $result[0], $result[1]);
        } elseif ($this->defaultScheme !== null && strpos($value, '://') === false) {
            $model->$attribute = $this->defaultScheme . '://' . $value;
        }
    }
public function validateAttribute($model, $attribute)
    {
        $value = $model->$attribute;
        $result = $this->validateValue($value);
        if (!empty($result)) {
            $this->addError($model, $attribute, $result[0], $result[1]);
        } elseif ($this->defaultScheme !== null && strpos($value, '://') === false) {
            $model->$attribute = $this->defaultScheme . '://' . $value;
        }
    }
{@inheritdoc}