How to use is_nan in combination with is_numeric to verify that the input is a number

In PHP, it is a common requirement to verify that user input is a valid number. Especially when processing form submissions, it is very important to make sure what the user enters is a number. PHP provides two useful functions: is_numeric() and is_nan() to help us verify input data.

What is is_numeric() ?

is_numeric() is a PHP built-in function to check if a variable is a numeric or a string of numeric characters. The function returns true if the variable is a numeric or a numeric string, and false if the variable is not a numeric string.

Example:

 <?php
$var = "123.45";

if (is_numeric($var)) {
    echo "$var It is a valid number";
} else {
    echo "$var 不It is a valid number";
}
?>

The above code will output 123.45 as a valid number , because the string "123.45" is considered a valid number.

What is is_nan() ?

is_nan() is a function used to check whether a variable is of type "Not a Number". Usually, is_nan() is used to verify that the numerical calculation returns an invalid number, such as the result of dividing by zero. It is worth noting that is_nan() can only act on numeric types, so for strings or other types, is_nan() will return false .

Example:

 <?php
$var = acos(8);  // acosThe parameter range of the function is-1arrive1，Out of range will returnNaN

if (is_nan($var)) {
    echo "turn outNaN";
} else {
    echo "结果It is a valid number";
}
?>

In this example, since the result of acos(8) is NaN, the output will be NaN .

How to combine is_numeric() and is_nan() to verify user input?

In actual development, users may enter various illegal data, such as empty strings, letters, special characters, etc. To ensure that the input is valid, we can use is_numeric() to determine whether the input is a number, and use is_nan() to ensure that the input does not become an invalid number (NaN). If the user inputs a number and is not calculated as NaN, we can think that the input is a valid number.

Sample code:

 <?php
// Get user input
$userInput = $_POST['user_input'];  // Assume that the data entered by the user passesPOSTMethod Submit

// Determine whether the input is a valid number
if (is_numeric($userInput) && !is_nan($userInput)) {
    echo "输入It is a valid number";
} else {
    echo "Invalid input，Please provide a valid number";
}
?>

In this example, first use is_numeric() to determine whether the input is a number. If it is a number, then use is_nan() to check whether the input is a valid number. This ensures that the input is both a number and is not an invalid "NaN" value.

Summarize

In PHP, is_numeric() and is_nan() are two very useful functions. is_numeric() helps us verify that the input is a valid number, while is_nan() ensures that the number we process is not an invalid NaN value. By combining these two functions, users' input can be more fully verified and invalid data can be avoided.