PHP is_nan() Function

Definition and Usage

NAN stands for "Not A Number". The is_nan() function checks whether its argument is not a number.

Syntax

is_nan ( float $val ) : bool

Parameters

Return Values

PHP is_nan() function returns TRUE if val is "not a number", otherwise it returns FALSE.

PHP Version

This function is available in PHP versions 4.x, PHP 5.x as well as PHP 7.x.

Example

Following example shows that 100 qualifies as NAN

<?php
   $val=100;
   $ret=is_nan($val);
   var_dump($val, $ret)
?>

Output

This will produce following result −

int(100)
bool(false)

Example

Value of log(0) is infinity. Following example verifies if it is NAN −

<?php
   $val=log(0);
   $ret=is_nan($val);
   var_dump($val, $ret);
?>

Output

This will produce following result −

float(-INF)
bool(false)

Example

Since cos(x) is between -1 and 1, acos() for parameter outside this range is NAN −.

<?php
   $val=acos(5);
   $ret=is_nan($val);
   var_dump($val, $ret);
?>

Output

This will produce following result −

float(NAN)
bool(true)

Example

Similarly sqrt(-1) produces NAN and hence is_nan() function returns true −

<?php
   $val=sqrt(-1);
   $ret=is_nan($val);
   var_dump($val, $ret);
?>

Output

This will produce following result −

float(NAN)
bool(true)