# is_nan

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

is_nanChecks whether a float is NAN

### Açıklama

is_nan(float `\$num`): bool

Returns whether the given `num` is `NAN` (Not A Number).

`NAN` is returned from mathematical operations that are undefined, for example when passing parameters outside of function’s input domain. The square root (sqrt()) is only defined for positive numbers, passing a negative number will result in `NAN`. Other examples of operations returning `NAN` are dividing `INF` by `INF` and any operation involving an existing `NAN` value.

Bilginize:

Despite its name of Not A Number, `NAN` is a valid value of type float.

Dikkat

`NAN` does not compare equal to `NAN`. To check whether a float is `NAN`, is_nan() must be used. Checking `\$float === NAN` will not work.

### Bağımsız Değişkenler

`num`

The float to check

### Dönen Değerler

`true` if `num` is `NAN`, else `false`.

### Örnekler

Örnek 1 is_nan() example

`<?php\$nan = sqrt(-1);var_dump(\$nan, is_nan(\$nan));?>`

Yukarıdaki örneğin çıktısı:

```float(NAN)
bool(true)```

### User Contributed Notes 4 notes

25
darkangel at moveinmod dot net
18 years ago
`nan/"not a number" is not meant to see if the data type is numeric/textual/etc..NaN is actually a set of values which can be stored in floating-point variables, but dont actually evaluate to a proper floating point number.The floating point system has three sections: 1 bit for the sign (+/-), an 8 bit exponent, and a 23 bit fractional part.There are rules governing which combinations of values can be placed into each section, and some values are reserved for numbers such as infinity. This leads to certain combinations being invalid, or in other words, not a number.`
14
10basetom
9 years ago
`I would use is_numeric() instead of ctype_digit() if you cannot be 100% sure what data type the string will be. Example from the docs:<?php\$numeric_string = '42';\$integer = 42;ctype_digit(\$numeric_string); // truectype_digit(\$integer); // false (ASCII 42 is the * character)is_numeric(\$numeric_string); // trueis_numeric(\$integer); // true?>`
ScorpioT1000
4 years ago
`function is_nan2(\$n) { return \$n !== \$n;}is_nan2(NAN); // true`
php at darkain dot com
8 years ago
`Starting with PHP 7, the string 'NaN' evaluates to the NaN value as well. Example:var_dump( (float) 'NaN' );PHP 5.x and HHVM:float(0)PHP 7.0:float(NAN)`