(PHP 4 >= 4.2.0, PHP 5)
is_infinite — 判断是否为无限值
$val
)
如果 val
为无穷大（正的或负的），例如 log(0)
的结果或者任何超出本平台的浮点数范围的值，则返回 TRUE。
val
要检查的值
如果 val
为无穷大返回 TRUE，否则返回 FALSE。
Anonymous (2012-05-02 16:55:39)
PHP_INT_MAX is The largest integer supported in this build of PHP. Usually int(2147483647). Available since PHP 4.4.0 and PHP 5.0.5
stangelanda at arrowquick dot com (2007-08-28 07:29:05)
Actually any string ending in INF is more appropriate than any string beginning with INF. Since negative infinity evaluates to "-INF" but it is still infinite. However in either case the STRING "INF" is not infinite, only a float that converts to "INF" or "-INF" is infinite.
A more appropriate function might be:
<?php
if (!is_defined('is_infinite')) { function is_infinite($val) {
return (is_float($val) and ("$val"=='INF' or "$val"=='-INF'));
} }
?>
* However the above function is untested.
(2006-08-21 08:54:29)
@ david,
That will return true for any string ending with "INF".
I think substr("$value",0,3) would be more appropriate.
david(@t)nirvanis(d@t)org (2004-08-31 02:49:30)
If you have PHP lower than 4.2 you can simulate the behaviour:
function is_infinite($value) {
return (substr("$value",-3) == "INF");
}
(tested on php 4.1.2)