(PHP 4 >= 4.2.0, PHP 5, PHP 7)
is_nan — Finds whether a value is not a number
is_nan ( float $val ) : bool
Checks whether val is 'not a number', like the result of acos(1.01).
val
The 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)
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https://www.php.net/manual/en/function.is-nan.php