is_finite() function in PHP

The is_finite() function checks if a value is finite or not. It returns true if the number is a finite number, else it returns false.

Syntax

is_finite(num)

Parameters

• num − The number to be checked.

Return Value

The is_finite() function returns true if num is a finite number, else it returns false.

Example 1: Finite Number

Let's check if a regular number is finite ?

<?php
    echo is_finite(1) ? 'true' : 'false';
?>

true

Example 2: Infinite Value

Let's check if log(0) (which is negative infinity) is finite ?

<?php
    echo is_finite(log(0)) ? 'true' : 'false';
?>

false

Example 3: Various Test Cases

Here are several examples showing different scenarios ?

<?php
    var_dump(is_finite(100));      // Normal number
    var_dump(is_finite(INF));      // Positive infinity
    var_dump(is_finite(-INF));     // Negative infinity
    var_dump(is_finite(NAN));      // Not a Number
    var_dump(is_finite(sqrt(-1))); // Square root of negative number
?>

bool(true)
bool(false)
bool(false)
bool(false)
bool(false)

Conclusion

The is_finite() function is useful for validating numeric values and ensuring they are within normal range. It returns false for infinity, negative infinity, and NaN values.