Php true/false values and conditions.

Question

just a simple question: which values give true and which false...
Know which in js...but this course can't give me answers even on half of my questuons :D
how about Undefined,NaN,null...
What will be result of comparing them...
Type of this things....

Yeah..I google it up tomorrow anyway...
But I guess you'll help others too :D
Cause this is realy important thing...

Answer 1

True 1,False 0.Undefined NaN and NULL totally specific things if you control a variable if its NULL you should write var=='NULL'

Answer 2

Yeah...that's simple...but I was talkin' about other thing.

1.Which exectly values will give us 1 or 0.

As example in js : any values exept undefined,null , NaN , "",0 will output false if we'll convert values into boolean type.

How about php ?

And other part:
2.What about comparing NaN with NaN,
Undefined with Undefined
or null with null...

And null with NaN e.t.c.

That's realy important thing everyone should know as i think.
At least in js it's so.

3.What about types of NaN,Undefined,null ?

Answer 3

only 0 will give you 0 value other values except NaN undef or NULL will give you value 1 like 23000 will give you value 1
as for NaN or NULL controls as i said you control them like this:"var=='NaN'or'NULL'"

Answer 4

and they all have uniqe types

Answer 5

so...
0,undefined,NaN,null - 0 ;
Any others 1 ?
even empty string ?

About control : user can input "NaN" or "Undefined",so var==NaN\Undefined just will not work here,exept we'll use ===...
But even about it - not so sure,about how it works here.

more about control:
Is there way to control this special types for sure ?

and still:

What about comparing special types ?