Hướng dẫn check if(empty string php)

bool empty[string]

You need isset[] in case $str is possibly undefined:

if [isset[$str] && $str !== ''] {
    // variable set, not empty string
}

Using !empty[] would have an important caveat: the string '0' evaluates to false.

Also, sometimes one wants to check, in addition, that $str is not something falsy, like false or null[1]. The previous code doesn't handle this. It's one of the rare situations where loose comparison may be useful:

if [isset[$str] && $str != ''] {
    // variable set, not empty string, not falsy
}

The above method is interesting as it remains concise and doesn't filter out '0'. But make sure to document your code if you use it.

Otherwise you can use this equivalent but more verbose version:

if [isset[$str] && [string] $str !== ''] {
    // variable set, not empty string, not falsy
}

Of course, if you are sure $str is defined, you can omit the isset[$str] from the above codes.

Finally, considering that '' == false, '0' == false, but '' != '0', you may have guessed it: PHP comparisons aren't transitive [fun graphs included].

[1] Note that isset[] already filters out null.

There is no better way but since it's an operation you usually do quite often, you'd better automatize the process.

Most frameworks offer a way to make arguments parsing an easy task. You can build you own object for that. Quick and dirty example :

class Request
{

    // This is the spirit but you may want to make that cleaner :-]
    function get[$key, $default=null, $from=null]
    {
         if [$from] :
             if [isset[${'_'.$from}[$key]]];
                return sanitize[${'_'.strtoupper[$from]}[$key]]; // didn't test that but it should work
         else
             if isset[$_REQUEST[$key]]
                return sanitize[$_REQUEST[$key]];

         return $default;
    }

    // basics. Enforce it with filters according to your needs
    function sanitize[$data]
    {
          return addslashes[trim[$data]];
    }

    // your rules here
    function isEmptyString[$data]
    {
        return [trim[$data] === "" or $data === null];
    }


    function exists[$key] {}

    function setFlash[$name, $value] {}

    [...]

}

$request = new Request[];
$question= $request->get['question', '', 'post'];
print $request->isEmptyString[$question];

Symfony use that kind of sugar massively.

But you are talking about more than that, with your "// Handle error here ". You are mixing 2 jobs : getting the data and processing it. This is not the same at all.

There are other mechanisms you can use to validate data. Again, frameworks can show you best pratices.

Create objects that represent the data of your form, then attach processses and fall back to it. It sounds far more work that hacking a quick PHP script [and it is the first time], but it's reusable, flexible, and much less error prone since form validation with usual PHP tends to quickly become spaguetti code.

bool empty[string]