is_nan math function to check if the input is number or not in PHP

PHP Math functions is_nan

bool is_nan ( float $input )

Parameter	DESCRIPTION
$input	Required : Number to check.

The output is TRUE if $input is 'not a number', else False.

We can check a input or variable is a number or not by using is_nan function. Note that we can't check a string with this function.
We can check square root of a negative number with is_nan function. Here is a sample code to check.


$v = acos(1.1);

if(is_nan($v)){

echo "this is not a number";

}else{

echo "this is a number";

}

Out put is

this is not a number

You can change the line $v=acos(1.1) with different values of variable $v and see the result.

$v=5.23; // this is a number

$v=4; // this is a number

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