CODEWITHSUNDEEP
phpconstants
Shlomi Hassid
Shlomi Hassid

Reputation: 6606

Why is it that PHP constants declared as case insensitive can be reassigned?

Lately I found a bug in a huge system I'm working on caused by this behaviour:

Consider this:

define('TEST',10);

echo TEST; // prints 10

define('TEST',20); // Error -> already assigned.

But if we declare it as insensitive:

define('TEST',10,true);

echo TEST; // prints 10

define('TEST',20); // no error ????

echo TEST; //prints 20

I understand what are the differences between CS and CI and I realise that I'm creating a new constant in the second definition. But I really don't understand why is that possible?

Isn't that a violation of the constant concept? Does this behaviour has any applications or is it a PHP weird thing...

Upvotes: 1

Views: 1514

Answers (2)

Rizier123
Rizier123

Reputation: 59691

Because your first constant (which you saved as case-insensitive) is saved in lowercase as you can read it in the manual:

Note: Case-insensitive constants are stored as lower-case.

Means since it is case-insensitive all variants of lower and upper case from test, which are != TEST in uppercase are corresponding to the value 10. If it is TEST which is case-sensitive means every letter in uppercase it is the constant with the value 20.

E.g.

Test -> 10
tEst -> 10
tesT -> 10
TEST -> 20

And a "special case" is also TEST if you use it before you define your case-sensitive constant it is still pointing to the constant with the value 10.

Upvotes: 4

Sougata Bose
Sougata Bose

Reputation: 31749

When you are doing define('TEST',10,true); it is stored in lower case but you can access them by both test & TEST.

Now there is no constant with the name of TEST. So when your defining it again the value is set to the constant.

Check it here

Upvotes: 0

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