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 — Prüft ob ein Wert keine Zahl ist
Beschreibung
bool is_nan
( float $val
)
Prüft ob der Parameter val keine darstellbare Zahl ist, wie z.B. das Ergebnis von acos(1.01).
Parameter-Liste
- val
-
Der zu prüfende Wert
Rückgabewerte
Liefert TRUE wenn val keine darstellbare Zahl ist, sonst FALSE.
add a note
User Contributed Notesis_nan
darkangel at moveinmod dot net
01-Mar-2006 10:04
01-Mar-2006 10:04
Sku
04-Dec-2005 01:29
04-Dec-2005 01:29
Hi nez,
better would be:
function isNaN( $var ) {
return !ereg ("^[-]?[0-9]+([\.][0-9]+)?$", $var);
}
ys, Sku
nez [at] NOSPAM gazeta [dot] pl
26-Sep-2005 01:27
26-Sep-2005 01:27
Paul, i guess better would be:
function isNaN( $var ) {
return ereg ("^[-]?[0-9]+([\.][0-9]+)?$", $var);
}
Vincent
23-Feb-2005 06:04
23-Feb-2005 06:04
Since NaN is not even equal to itself, here is a way to test it:
<?php
function my_is_nan($_) {
return ($_ !== $_);
}
?>