Is there any legitimate use for bare strings in PHP?

问题

This question got me thinking about bare strings.

When PHP sees a string that's not enclosed in quotes, it first checks to see if it's a constant. If not, it just assumes it's a string and goes on anyway. So for example if I have

echo $foo[bar];

If there's a constant called bar it uses that for the array key, but if not then it treats bar as a bare string, so it behaves just like

echo $foo["bar"];

This can cause all kinds of problems if at some future date a constant is added with the same name.

My question is, is there any situation in which it actually makes sense to use a bare string?

回答1:

Nope, I can not see a single instance where it would make sense, and it always is dangerous. Using strings without quotes should absolutely be reserved to address constants. I don't understand how the inventors of PHP could decide to introduce this ridiculous behaviour at all - it makes the proper use of constants almost impossible (because if you try to access a constant that has not been defined, PHP will silently and stupidly generate a string) without giving any benefit.

回答2:

This doesn't probably count as legitimate, but my friend's tweetable proof-of-concept MVC framework, TweetMVC eschews quotes in a few spots to squeeze a few more characters in, e.g.:

foreach(c('mod')as$f)require"t/$f.php";@list($c,$m,$a)=explode('/',@$_GET[r],3);$c=$c?:c('dc');$o=(@include"c/$c.php")?@new$c($m,$a):e(1)

回答3:

The only time you would use a bare string as a key is if it's been previously used in define() for a constant.

来源：https://stackoverflow.com/questions/2406006/is-there-any-legitimate-use-for-bare-strings-in-php