How to use is_nan function to detect invalid values in calculation results

gitbox 2025-05-27

In PHP, we often need to perform various mathematical operations, and the results of these operations may sometimes contain invalid numerical values, such as "non-numerical values" (NaN). The is_nan() function is used to detect whether the calculation result is in a "non-numeric" state. It is very useful when processing calculations that may return invalid values. This article will introduce how to use the is_nan() function to detect invalid values in the calculation results, and use examples to illustrate how to avoid calculation errors.

What is NaN (Not a Number)?

In floating point calculations, NaN represents an invalid value. For example, in mathematics, the result of 0/0 is an invalid numeric value, which has no practical meaning, so it returns NaN . NaN is usually generated in PHP by calculation errors or impossible mathematical operations such as zero-dividing zero.

In PHP, the is_nan() function is used to determine whether a value is NaN. is_nan() will return true only if the parameter is NaN, otherwise false .

How to use is_nan() function

 <?php
// Example 1：use is_nan Function judgment NaN value
$val1 = sqrt(-1);  // Calculate the square root of a negative number，The result is NaN
if (is_nan($val1)) {
    echo "val1 It&#39;s one NaN value。\n";
} else {
    echo "val1 no NaN。\n";
}

// Example 2：0 Divide by 0 的The result is NaN
$val2 = 0 / 0;
if (is_nan($val2)) {
    echo "val2 It&#39;s one NaN value。\n";
} else {
    echo "val2 no NaN。\n";
}

// Example 3：Valid numbers
$val3 = 10 / 2;  // turn out 5
if (is_nan($val3)) {
    echo "val3 It&#39;s one NaN value。\n";
} else {
    echo "val3 no NaN。\n";
}
?>

Output result:

 val1 It&#39;s one NaN value。
val2 It&#39;s one NaN value。
val3 no NaN。

How to avoid NaN errors?

Although PHP can detect NaN values through the is_nan() function, in development, we often want to avoid these invalid values appearing in the calculation. To avoid the generation of NaN values, possible error operations can be detected and pre-processed. Here are some common ways to avoid NaN errors:

Check whether the divisor is zero : When performing a division operation, first make sure that the divisor is not zero.
Handle invalid mathematical operations : For example, when using the sqrt() function, make sure that the passed in value is non-negative.
Verify the result : use is_nan() to determine whether the calculation result is NaN. If so, corresponding error handling measures will be taken.

Example: Avoid zero-deletion operation

 <?php
// Prevent de-zero errors
$numerator = 10;
$denominator = 0;

if ($denominator == 0) {
    echo "mistake：Divider is zero，Unable to perform division operation。\n";
} else {
    $result = $numerator / $denominator;
    if (is_nan($result)) {
        echo "计算The result is NaN。\n";
    } else {
        echo "计算turn out：$result\n";
    }
}
?>

Summarize

is_nan() is a very useful function in PHP that can help us detect invalid values in the calculation results. When performing mathematical operations, especially when it comes to operations such as division and root signs, we should be careful to deal with the situations where NaN may be generated. By using the is_nan() function, we can avoid the impact of invalid values on program logic and ensure the stability and reliability of program operation.

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