php 编译错误：不能对表达式的结果使用 isset()
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Compile Error: Cannot use isset() on the result of an expression
提问by ReynierPM
I'm getting this error in a app I am migrating from SF2.0.x to SF2.7:
我在从 SF2.0.x 迁移到 SF2.7 的应用程序中收到此错误：
[1] Symfony\Component\Debug\Exception\FatalErrorException: Compile Error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead)
at n/a
in /var/www/html/reptooln_admin/app/cache/dev/twig/68/7f/63589dd3687cb849dd68e6b6c10aa99eda1d82f95a5f3ac52a864d200499.php line 39
I don't know what is failing or how to fix this so I need some advise. This is the line at cache file where the Stacktrace is reported:
我不知道出了什么问题或如何解决这个问题，所以我需要一些建议。这是报告 Stacktrace 的缓存文件中的行：
if ((((empty((isset($context["form_action"]) ? $context["form_action"] : $this->getContext($context, "form_action"))) == true) || (isnull((isset($context["form_action"]) ? $context["form_action"] : $this->getContext($context, "form_action"))) == true)) || (isset((isset($context["form_action"]) ? $context["form_action"] : $this->getContext($context, "form_action"))) == false))) {
echo " ";
$context["form_action"] = "";
echo " ";
What I have this TwigExtension:
我有这个 TwigExtension：
class PDOneTwigExtension extends \Twig_Extension
{
public function getFilters()
{
return array(
'var_dump' => new \Twig_Filter_Function('var_dump'),
'empty' => new \Twig_Filter_Function('empty', array($this, 'is_empty')),
'isset' => new \Twig_Filter_Function('isset', array($this, 'is_set')),
'isnull' => new \Twig_Filter_Function('isnull', array($this, 'is_null')),
'ucfirst' => new \Twig_Filter_Function('ucfirst', array($this, 'uc_first')),
'ucwords' => new \Twig_Filter_Function('ucwords', array($this, 'uc_words')),
'count' => new \Twig_Filter_Function('count', array($this, 'co_unt')),
'sizeof' => new \Twig_Filter_Function('sizeof', array($this, 'size_of')),
'concat' => new \Twig_Filter_Function('concat', array($this, 'concat')),
'in_array' => new \Twig_Filter_Function('in_array', array($this, 'inarray')),
'array' => new \Twig_Filter_Function('array', array($this, 'array_')),
'add_to_array' => new \Twig_Filter_Function('add_to_array', array($this, 'add_to_array')),
'replace' => new \Twig_Filter_Function('replace', array($this, 'replace')),
'htmlentitydecode' => new \Twig_Filter_Function('htmlentitydecode', array($this, 'htmlentitydecode'))
);
}
public function is_empty($sentence)
{
return empty($sentence) ? true : false;
}
// rest of methods goes here
public function getName()
{
return 'pdone_twig_extension';
}
}
And I'm using at template as follow:
我在模板中使用如下：
{% if form_action|empty == true or form_action|isnull == true or form_action|isset == false %} {% set form_action = '' %} {% endif %}
Where could be the issue here? Any advice?
这里可能是哪里出了问题？有什么建议吗？
回答by Dan Blows
From documentation:
从文档：
isset() only works with variables as passing anything else will result in a parse error.
isset() 仅适用于变量，因为传递任何其他内容都会导致解析错误。
You're not directly passing a variable to isset(). So you need to calculate the value first, assign it to a variable, and then pass that to isset().
您没有直接将变量传递给isset(). 因此，您需要先计算该值，将其分配给一个变量，然后将其传递给isset().
For example, what you're doing at the moment is something like:
例如，你现在正在做的事情是这样的：
if(isset($something === false)) { } // throws a parse error, because $something === false is not a variable
What you need to do instead is:
你需要做的是：
$something = false;
if(isset($something)) { ... }
回答by Alex
Why are you doing so much useless code?
你为什么要写这么多无用的代码？
Why don't just:
为什么不只是：
{% if form_action|empty == true %} {% set form_action = '' %} {% endif %}
