Opencart中的语法错误期望标识符

Question

I was just checking functionality of opencart's cart controller. Where i saw

foreach ($results as $result) {
                if ($this->config->get($result['code'] . '_status')) {
                    $this->load->model('total/' . $result['code']);
                    $this->{'model_total_' . $result['code']}->getTotal($total_data, $total, $taxes);
                }
            } 

Its working fine. But when i change it to

foreach ($results as $result) {
                if ($this->config->get($result['code'] . '_status')) {
                    $this->load->model('total/' . $result['code']);
                    $this->'model_total_' . $result['code']->getTotal($total_data, $total, $taxes);
                    }
            } 

its giving me an error Parse error: syntax error, unexpected ''model_total_'' . I don't know why this happened. Does it refer to same or not. If not then why i have to use curly braces $this->{'model_total_' . $result['code']} $this->{'model_total_' . $result['code']} for it. Can anyone explain.

Answer 1

It is not accepting the concatenation of your result there, so try this,

foreach ($results as $result) {
     if ($this->config->get($result['code'] . '_status')) {
         $this->load->model('total/' . $result['code']);
         $code = 'model_total_' . $result['code'];
         $this->$code->getTotal($total_data, $total, $taxes);
     }
}

or

foreach ($results as $result) {
     if ($this->config->get($result['code'] . '_status')) {
         $this->load->model('total/' . $result['code']);
         $this->{'model_total_' . $result['code']}->getTotal($total_data, $total, $taxes); // wrap with {}
     }
}

EDIT

Wrapping with {} is required when you are using array element for concatenation.

$this->'model_total_' . $result['code']->getTotal($total_data, $total, $taxes);
                        ^             ^

you are using array element for concatenation, So you are getting error.

You can even notice that my first example works without {} , because its normal variable.

Answer 2

如果要使用表达式作为属性名称，则必须将其放在{}除非它只是一个变量。