I have tested the
is_numeric function in the
NAN constant in PHP and the given result
is_numeric(NAN); // TRUE
But NAN means “Not A Number”. Why the function
I know that NAN is of
float type. But when testing the two cases below, the results are different:
is_float(NAN) // true filter_var(NAN, FILTER_VALIDATE_FLOAT)// false
Why ocurred it?
Sorry, my english is bad
NAN is a special constant. It has to hold some value, so it holds a
var_dump(NAN); // float(NAN);
The problem is that
filter_var isn’t comparing data types, it’s looking for numbers, which
NAN is not.
Some numeric operations can result in a value represented by the constant NAN. This result represents an undefined or unrepresentable value in floating-point calculations. Any loose or strict comparisons of this value against any other value, including itself, will have a result of FALSE.
Because NAN represents any number of different values, NAN should not be compared to other values, including itself, and instead should be checked for using is_nan().
NAN is a non-zero floating point value. What is NAN, Its a square root of
So now it comes to complex numbers. Square root of
-i which means NAN can have two values. So if
NAN were to evaluate to
NAN == false would become true instead.