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)
is_infinite
(PHP 4 >= 4.2.0, PHP 5, PHP 7)
is_infinite — Finds whether a value is infinite
Description
bool is_infinite
( float
$val
)
Returns TRUE if val is infinite (positive or
negative), like the result of log(0) or any value too
big to fit into a float on this platform.
Parameters
-
val -
The value to check
Return Values
TRUE if val is infinite, else FALSE.
See Also
- is_finite() - Finds whether a value is a legal finite number
- is_nan() - Finds whether a value is not a number
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User Contributed Notes 5 notes
david(@t)nirvanis(d@t)org ¶
13 years ago
stangelanda at arrowquick dot com ¶
10 years ago
Actually any string ending in INF is more appropriate than any string beginning with INF. Since negative infinity evaluates to "-INF" but it is still infinite. However in either case the STRING "INF" is not infinite, only a float that converts to "INF" or "-INF" is infinite.
A more appropriate function might be:
<?php
if (!is_defined('is_infinite')) { function is_infinite($val) {
return (is_float($val) and ("$val"=='INF' or "$val"=='-INF'));
} }
?>
* However the above function is untested.
Anonymous ¶
11 years ago
@ david,
That will return true for any string ending with "INF".
I think substr("$value",0,3) would be more appropriate.
espertalhao04 at hotmail dot com ¶
4 years ago
fastest version to php <4.2:
<?php function is_infinite($v){$v=$v>>0;return -9e1000==$v||$v==9e1000;}; ?>
the $v=$v>>0; is just to ensure it is a number and its not mandatory.
effectively, the function can be reduced to:
<?php function is_infinite($v){return -9e1000==$v||$v==9e1000;}; ?>
this works because any number that is too big or too small for a float is considered to be infinite or -infinite.
