PHP is_nan() Function

Check whether a value is 'not-a-number':

<?php
echo is_nan(200) . "<br>";
echo is_nan(acos(1.01));
?>

Definition and Usage

The is_nan() function checks whether a value is 'not a number'.

This function returns true (1) if the specified value is 'not-a-number', otherwise it returns false/nothing.

is_nan( value);

Parameter	Description
value	Required. Specifies the value to check

Return Value:	TRUE if value is 'not a number', FALSE otherwise
Return Type:	Boolean
PHP Version:	4.2+