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In PHP, is_nan() and is_finite() are two commonly used numerical detection functions, which are used to determine whether a variable is a non-numerical (NaN) or whether a numerical value is finite. Although they look similar, they have different uses and applicable scenarios. This article will discuss in detail the differences between these two functions and their respective application scenarios.
The is_nan() function is used to detect whether a value is a "non-numeric" (NaN, Not-a-Number). In mathematics and computer science, NaN is a special floating value that usually represents a result that cannot be expressed as a numerical value. For example, when 0 is divided by 0 or calculating the square root of a negative number, NaN is generated.
is_nan(mixed $var): bool
Parameters : $var can be any type of variable.
Return value : if $var is NaN, the function returns true , otherwise false .
$number1 = sqrt(-1); // Calculate the square root of a negative number，The result isNaN
$number2 = 10 / 0; // The result isINF，The Great
var_dump(is_nan($number1)); // Output：bool(true)
var_dump(is_nan($number2)); // Output：bool(false)
is_nan() is very suitable for scenarios where invalid results appear in calculations, especially when floating point operations are involved. For example:
In mathematical calculations, avoid invalid results caused by operations such as dividing by zero or negative numbers.
In the fields of scientific computing, image processing, etc., whether there are illegal results.
The is_finite() function is used to check whether a number is a finite value. It checks whether the given number is a finite value, cannot be infinity (INF) or NaN.
is_finite(mixed $var): bool
Parameters : $var can be any type of variable.
Return value : If $var is a finite value, the function returns true , otherwise false .
$number1 = 10 / 2; // The result is5
$number2 = 10 / 0; // The result isINF
$number3 = sqrt(-1); // The result isNaN
var_dump(is_finite($number1)); // Output：bool(true)
var_dump(is_finite($number2)); // Output：bool(false)
var_dump(is_finite($number3)); // Output：bool(false)
is_finite() is very suitable for detecting whether a variable is a finite number, especially in the fields of scientific computing, financial applications, etc. It can be used to determine whether the calculation result is valid and avoid abnormal program behavior caused by infinity (INF) or NaN.
Different judgment objects :
is_nan() only checks whether it is NaN.
is_finite() checks whether it is a finite value, it returns false if it is NaN or Infinity (INF).
Different scenarios apply :
is_nan() is suitable for checking whether there are invalid numerical calculations, such as 0 divided by 0.
is_finite() is suitable for checking whether the value is limited and avoiding infinity or NaN affecting the program logic.
The return result is different :
is_nan() returns true only if the variable is NaN.
is_finite() returns false not only NaN, but also INF (infinity).
$value1 = 0 / 0; // NaN
$value2 = 10 / 0; // INF
echo is_nan($value1); // true
echo is_nan($value2); // false
echo is_finite($value1); // false
echo is_finite($value2); // false
The is_nan() function is used to determine whether a variable is NaN (non-numerical), and is suitable for checking invalid numerical calculations.
The is_finite() function is used to check whether a number is finite and is suitable for judging whether the value is valid and avoid interference from infinity or NaN.
In actual development, choosing which function to use depends on the type of numerical value you need to check and your application scenario. Generally, is_nan() prefers special error handling, while is_finite() is used for numerical legality checks.
