is_nan
(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)
Checks whether a float is NAN
Description
Returns whether the given num is NAN (Not A Number).
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.
Despite its name of Not A Number, NAN is a valid value of type Float.
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
numThe Float to check
Return Values
true if num is NAN, else false.
Examples
is_nan() example
<?php
$nan = sqrt(-1);
var_dump($nan, is_nan($nan));
?>The above example will output:
float(NAN)
bool(true)