Zend Certification PHP 5 : Difference between isset() and other is_*() functions

[oggy]

Hello
I try to answer this question for the Zend Certification PHP 5 :
"What is the difference between isset() and other is_*() functions
(is_alpha(), is_number(), etc.)?"

Do you have a solution ?

Thanks

[ZeldorBlat]

oggy wrote:

Hello
I try to answer this question for the Zend Certification PHP 5 :
"What is the difference between isset() and other is_*() functions
(is_alpha(), is_number(), etc.)?"

Do you have a solution ?

Thanks

Read this:
<http://www.php.net/isset>

In particular the warning that "isset() only works with variables as
passing anything else will result in a parse error" and the note that
"Because this is a language construct and not a function, it cannot be
called using variable functions."

[oggy]

thanks a lot
"isset() only works with variables" means that its not working with
constants (only).

On 27 déc, 20:21, "ZeldorBlat" <[e-mail]:

oggy wrote:

Hello
I try to answer this question for the Zend Certification PHP 5 :
"What is the difference between isset() and other is_*() functions
(is_alpha(), is_number(), etc.)?"

Do you have a solution ?

ThanksRead this:

<http://www.php.net/isset>

In particular the warning that "isset() only works with variables as
passing anything else will result in a parse error" and the note that
"Because this is a language construct and not a function, it cannot be
called using variable functions."

[ZeldorBlat]

oggy wrote:

thanks a lot
"isset() only works with variables" means that its not working with
constants (only).

That's half of it. The other half is that it won't work with the
return value of a function call (directly). Consider the following:

function foo() {
return 1;
}

//This is ok:
$x = foo();
isset($x);

//But this throws a fatal error:
isset(foo());