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    is_nan

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

    is_nan — Encuentra si un valor no es un número

    Descripción

    is_nan(float $val): bool

    Verifica si val no es un numero, como por ejemplo el resultado de acos(1.01).

    Parámetros

    val

    El valor a revisar

    Valores devueltos

    Devuelve true si val no es un número, en caso contrario devuelve false.

    Ejemplos

    Ejemplo #1 Ejemplo de is_nan()

    <?php
    // Invalid calculation, will return a
    // NaN value
    $nan = acos(8);

    var_dump($nan, is_nan($nan));
    ?>

    El resultado del ejemplo sería:

    float(NAN)
bool(true)

    Ver también

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    User Contributed Notes 7 notes

    up
    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.
    up
    13
    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($numeric_string);  // true
    ctype_digit($integer);         // false (ASCII 42 is the * character)

    is_numeric($numeric_string);   // true
    is_numeric($integer);          // true
    ?>
    up
    3
    ScorpioT1000
    4 years ago
    function is_nan2($n) {
        return $n !== $n;
    }

    is_nan2(NAN); // true
    up
    1
    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)
    up
    -12
    modern dot apocalypse at gmail dot com
    12 years ago
    I have decided to do some testing because I am getting unusual results with the is_nan function and here are the results of my tests:

    <?php
    var_dump    (NAN); // float NAN

    var_dump(NAN == NAN); // boolean true
    var_dump(NAN === NAN); // boolean true
    var_dump(is_nan(NAN)); // boolean true

    var_dump(NAN == 12); // boolean true
    var_dump(NAN === 12); // boolean false
    var_dump(is_nan(12)); // boolean false

    var_dump(NAN == 12.4); // boolean true
    var_dump(NAN === 12.4); // boolean true
    var_dump(is_nan(12.4)); // boolean false

    var_dump(NAN == NULL); // boolean true
    var_dump(NAN === NULL); // boolean false
    var_dump(is_nan(NULL)); // boolean false

    var_dump(NAN == 'K<WNPO'); // boolean true
    var_dump(NAN === 'K<WNPO'); // boolean false
    var_dump(is_nan('K<WNPO')); // null and throws a warning "Warning: is_nan() expects parameter 1 to be double, string given in NANTest.php on line 13"
    up
    -9
    J.K.
    15 years ago
    For seeing whether or not something is a number, use ctype_digit().
    up
    -10
    php at keith tyler dot com
    14 years ago
    It seems odd to me, but in boolean context, NAN evalutes to true.

    <?php
    var_dump    (acos(8));
    var_dump((bool)acos(8));
    ?>

    Returns:

    float(NAN)
    bool(true)

    Incidentally INF and -INF also evaluate to true.
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