is_nan
Checks whether a float is NAN
Description
bool is_nan(float $num)
NAN is returned from mathematical operations that are undefined,
for example when passing parameters outside of function’s input domain. The square root
(sqrt) is only defined for positive numbers, passing a negative number
will result in NAN. Other examples of operations returning NAN
are dividing INF by INF and any operation involving an
existing NAN value.
Note:
Despite its name of Not A Number
, NAN is a valid value of type float.
Caution
NAN does not compare equal to NAN. To check whether
a float is NAN, is_nan must be used. Checking
$float === NAN will not work.
Parameters
-
num
-
The float to check
Return Values
true if num is NAN, else false.
Examples
Example #1 is_nan example
<?php
$nan = sqrt(-1);
var_dump($nan, is_nan($nan));
?>
The above example will output: