PHP is_nan(): check for the NAN floating-point value

Check specifically for NAN

is_nan() checks whether a floating-point value is the special NAN (not-a-number) value. It is not a general numeric-input validator.

$value = sqrt(-1);
var_dump(is_nan($value)); // bool(true)

Use is_nan() only for the special floating-point NAN value; use is_numeric() when validating numeric strings or general input.

var_dump(is_nan(4.0));              // bool(false)
var_dump(is_nan(4.78));             // bool(false)
var_dump(is_nan(acos(2)));          // bool(true)

Syntax

bool is_nan(float $num)

Parameter	DESCRIPTION
`$num`	Required: float value to check.

Returns true only when the float is NAN; otherwise it returns false.

is_nan() is not a general numeric validator. It is intended for floating-point results such as sqrt(-1) or acos(2) that produce NAN.

$v = acos(1.1);
if(is_nan($v)){
echo "this is not a number";
}else{
echo "this is a number";
}

Output is here. More about acos()

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<br>
$v=4; // this is a number

Getting the output by using var_dump()

var_dump(is_nan(4.0));             // bool(false)
var_dump(is_nan(sqrt(-1)));       // bool(true)

Questions

What does the is_nan() function in PHP do?
What is the purpose of the is_nan() function in PHP?
What is the return value of the is_nan() function?
How can you use the is_nan() function to check if a variable contains a NaN (Not a Number) value?
What are some examples of values that would return true when passed to the is_nan() function?
How does the is_nan() function differ from the isNaN() function in JavaScript?
Can you use the is_nan() function to check if a string is a valid number?
How can you handle scenarios where a mathematical operation in PHP may result in a NaN value?
Are there any alternative approaches to check if a value is NaN without using the is_nan() function?
Is the is_nan() function limited to specific data types, or can it work with different types of variables?

Math Functions is_finite(): check finite values is_infinite(): check infinity

Subhendu Mohapatra

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is_nan() : whether a value is not a number

Check specifically for NAN

Questions

Subhendu Mohapatra