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I am told that good developers can spot/utilize the difference between Null and False and 0 and all the other good "nothing" entities.
What is
the difference, specifically in PHP? Does it have something to do with ===?
Ben
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asked Sep 26, 2008 at 2:53
stalepretzelstalepretzel
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It's language specific, but in PHP :
Null means "nothing". The var has not been initialized.
False means "not true in a boolean context". Used to explicitly show you are dealing with logical issues.
0
is an int. Nothing to do with the rest above, used for mathematics.
Now, what is tricky, it's that in dynamic languages like PHP, all of them have a value in a boolean context, which [in PHP] is False.
If you test it with ==, it's testing the boolean value, so you will get equality. If you test it with ===, it will test the type, and you will get inequality.
So why are they useful ?
Well, look at the strrpos[] function. It
returns False if it did not found anything, but 0 if it has found something at the beginning of the string !
And of course, if you deal with states:
You want to make a difference between DebugMode = False [set to off], DebugMode = True [set to on] and DebugMode = Null [not set at all, will lead to hard debugging ;-]].
Robert
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answered Sep 26, 2008 at 11:50
e-satise-satis
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null is null. false is false. Sad but true.
there's not much consistency in PHP [though it is improving on latest releases, there's too much backward compatibility]. Despite the design wishing some consistency [outlined in the selected answer here], it all get confusing when you consider method returns that use false/null in not-so-easy to reason ways.
You will often see null being used when they are already using false for something. e.g. filter_input[]. They return false if the variable fails the filter, and null if the variable does not exists [does not existing means it also failed the filter?]
Methods returning false/null/string/etc interchangeably is a hack when the author care about the type of failure, for example, with filter_input[] you can check for ===false or ===null if you care why the validation failed. But if you don't it might be a pitfall as one might forget to add the check for ===null if they only remembered to write the test case for ===false. And most php unit test/coverage tools will not
call your attention for the missing, untested code path!
Lastly, here's some fun with type juggling. not even including arrays or objects.
var_dump[ 0 true [string match]
'*' === true -> false [numberic match]
[int]'*' == true -> false
[string]'*' == true -> true
PHP7 strictness is a step forward, but maybe not enough. //web-techno.net/typing-with-php-7-what-you-shouldnt-do/
answered Nov 4, 2018 at 12:02