is_infinite
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.
is_nan
(PHP 4 >= 4.2.0, PHP 5)
is_nan — Encuentra si un valor no es un número
Descripción
bool is_nan
( float
$val
)
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
- is_finite() - Encuentra si un valor es un número finito legal
- is_infinite() - Encuentra si un valor es infinito
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User Contributed Notes
is_nan - [7 notes]
darkangel at moveinmod dot net ¶
7 years ago
Sku ¶
7 years ago
Hi nez,
better would be:
function isNaN( $var ) {
return !ereg ("^[-]?[0-9]+([\.][0-9]+)?$", $var);
}
ys, Sku
modern dot apocalypse at gmail dot com ¶
1 year 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"
php at keith tyler dot com ¶
3 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.
nez [at] NOSPAM gazeta [dot] pl ¶
7 years ago
Paul, i guess better would be:
function isNaN( $var ) {
return ereg ("^[-]?[0-9]+([\.][0-9]+)?$", $var);
}