(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)
is_nan — Checks whether a float is NAN
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.
Note:
Despite its name of
Not A Number,NANis a valid value of type float.
Example #1 is_nan() example
<?php
$nan = sqrt(-1);
var_dump($nan, is_nan($nan));
?>The above example will output:
float(NAN) bool(true)