is_nan
(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)
is_nan — Checks whether a float is NAN
Description
is_nan(float $num): boolReturns 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.
Note:
Despite its name of
Not A Number,NANis 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:
float(NAN)
bool(true)
See Also
- is_finite() - Checks whether a float is finite
- is_infinite() - Checks whether a float is infinite
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Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/function.is-nan.php