is_finite

(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

is_finite — Checks whether a float is finite

Description

is_finite(float $num): bool

Returns whether the given num is a finite float.

A finite float is neither NAN (is_nan()), nor infinite (is_infinite()).

Parameters

num: The float to check

Return Values

true if num is none of NAN, INF, -INF, else false.

Examples

Example #1 is_finite() example

<?php
$float = 1.2345;
var_dump($float, is_finite($float));

$nan = sqrt(-1);
var_dump($nan, is_finite($nan));

$inf = 1e308 * 2;
var_dump($inf, is_finite($inf));
?>

The above example will output:

float(1.2345)
bool(true)
float(NAN)
bool(false)
float(INF)
bool(false)

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User Contributed Notes 1 note

down

Daniel Klein ¶

7 years ago

(is_finite($float)) is equivalent to (!is_infinite($float) && !is_nan($float)), i.e. a number can only be one of finite, infinite and NaN. You don't need to check both is_infinite() and is_nan() to see if a number is invalid or out of range.

<?php
$finite = 42;
$infinite = log(0);
$nan = acos(2);

var_dump(is_finite($finite), is_infinite($finite), is_nan($finite));  // true, false, false
var_dump(is_finite($infinite), is_infinite($infinite), is_nan($infinite));  // false, true, false
var_dump(is_finite($nan), is_infinite($nan), is_nan($nan)); // false, false, true
?>