问题
Is the following:
$arr = [
foo => 'bar',
bar => 'foo'
];
The same as:
$arr = [
'foo' => 'bar',
'bar' => 'foo'
];
In other words, is putting quotes on named indexes unnecessary? When would be the only times when putting quotes on string indexes be really needed?
回答1:
Your first example should throw a NOTICE. If you do not use quotes then PHP will look for a constant with that name.
php > $myArr = [abc => 'hello'];
PHP Notice: Use of undefined constant abc - assumed 'abc' in php shell code on line 1
PHP Stack trace:
PHP 1. {main}() php shell code:0
Notice: Use of undefined constant abc - assumed 'abc' in php shell code on line 1
Call Stack:
9.7779 350840 1. {main}() php shell code:0
I ran this example in PHP 7.1.8, however in PHP 7.2 this has been deprecated.
回答2:
PHP converts "bare strings" into proper strings, but will give you a warning. It is likely that this functionality will disappear in future.
If you really, really want to do this (you shouldn't), it will work as log as the string matches the format for a constant, which is the regex
[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*
(Don't do it. Just don't.)
来源:https://stackoverflow.com/questions/49365907/is-putting-quotes-on-php-named-indexes-unnecessary