(PHP 4 >= 4.2.0, PHP 5, PHP 7)
is_nan — 锟叫讹拷锟角凤拷为锟较凤拷锟斤拷值
$val
) : bool
锟斤拷锟� val 为"锟斤拷锟斤拷值"锟斤拷锟斤拷锟斤拷
acos(1.01) 锟侥斤拷锟斤拷锟斤拷蚍祷锟� TRUE锟斤拷
val要锟斤拷锟斤拷值
锟斤拷锟� val 锟斤拷锟斤拷一锟斤拷锟斤拷锟街ｏ拷not a number锟斤拷锟斤拷锟斤拷 TRUE锟斤拷锟斤拷锟津返伙拷 FALSE锟斤拷
Example #1 is_nan() 锟斤拷锟斤拷
<?php
// Invalid calculation, will return a
// NaN value
$nan = acos(8);
var_dump($nan, is_nan($nan));
?>
锟斤拷锟斤拷锟斤拷锟教伙拷锟斤拷锟斤拷锟�
float(NAN) bool(true)