PHP is_nan judges the intermediate results of mathematical calculations

In daily PHP development, especially in scenarios involving mathematical calculations, programmers may encounter a special value: NaN (Not a Number). NaN usually occurs in illegal mathematical operations, such as subtracting infinity from infinity, taking the square root of negative numbers, etc. NaN is more common in languages ​​such as JavaScript, while NaN also exists in PHP and can be judged by the is_nan() function.

What is NaN?

NaN is a special value in the IEEE 754 floating point number standard, indicating "not a number". It is usually not directly identified by ordinary numerical comparisons (for example == or === ), so it needs to be judged using special functions.

The use of is_nan() function

In PHP, the is_nan() function is used to determine whether a variable is NaN. The syntax is as follows:

 bool is_nan ( float $num )

This function receives a floating point parameter, which returns true if this value is NaN, otherwise false .

Typical examples

Here are some examples showing the practical use of is_nan() :

 <?php

// An illegal mathematical operation：Infinity minus Infinity
$a = log(0);  // -INF
$b = log(0);  // -INF
$c = $a - $b; // The result is NaN

if (is_nan($c)) {
    echo "turn out NaN";
} else {
    echo "The result is not NaN";
}
?>

In this example, log(0) returns negative infinity (-INF), and the result of two negative infinity subtraction is not a definite number, so PHP will return NaN. This result can be successfully judged using is_nan() .

Things to note

1. is_nan() is not used to detect whether a string or integer is an "illegal value" , it only applies to floating point numbers.

2. In actual business, the emergence of NaN often means that there are problems with a certain mathematical logic, and the program should be captured and processed in a timely manner.

3. When using is_nan() , make sure that the parameter is a floating point number, otherwise the expected result may not be returned.

Application scenario: Verification of interface calculation results

Suppose you develop an API for receiving two numbers and calculating their ratios:

 <?php

function calculate_ratio($a, $b) {
    if ($b == 0) {
        return NAN;
    }
    return $a / $b;
}

$result = calculate_ratio(10, 0);

if (is_nan($result)) {
    echo "Invalid calculation result，Please check the parameter input。";
} else {
    echo "The ratio is：$result";
}
?>

In the above code, if the divisor is 0, we actively return NAN and use is_nan() to determine whether it is an illegal value. This approach is very practical in some numerical computing interfaces, which can avoid directly returning false results or triggering runtime errors.

URL situations involved in the example

Suppose you want to submit a computation request through the interface, for example:

 $apiUrl = 'https://gitbox.net/api/calculate';

You can use CURL or file_get_contents() to send requests to services under the gitbox.net domain name, and use is_nan() to judge the return result to ensure the reliability of the calculation logic.

Summarize

Although PHP is not the preferred language for mathematical calculations, NaN values ​​may appear quietly when dealing with tasks involving floating-point operations. With the help of the is_nan() function, developers can effectively identify these potential problems, thereby enhancing the robustness of the code. Understanding and rational use of is_nan() is particularly critical to ensuring the numerical accuracy of the system.