(PHP 4 >= 4.2.0, PHP 5, PHP 7)
is_nan — Finds whether a value is not a number
$val
) : bool
Checks whether val is 'not a number',
like the result of acos(1.01).
valThe value to check
Returns TRUE if val is 'not a number',
else FALSE.
Example #1 is_nan() example
<?php
// Invalid calculation, will return a
// NaN value
$nan = acos(8);
var_dump($nan, is_nan($nan));
?>
The above example will output:
float(NAN) bool(true)