is_nan
(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)
is_nan — Checks whether a float is NAN
Description
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
Examples
Example #1 is_nan() example
<?php
$nan = sqrt(-1);
var_dump($nan, is_nan($nan));
?>
The above example will output:
