is_numeric() function in PHP: How to check if a variable is numeric

In PHP, it is often necessary to judge and verify the data type of variables. Among them, determining whether a variable is of numeric type is a very common operation. PHP provides a built-in function is_numeric() to check whether a variable is of numeric type.

The usage format of is_numeric() function is as follows:

bool is_numeric (mixed $var)

Among them, $var is the variable that needs to be checked, it can be any PHP data Type, including string, integer, floating point, etc. When $var is a number or numeric string, the is_numeric() function returns true, otherwise it returns false.

Below we use specific code examples to illustrate the use of the is_numeric() function.

1. Check integer variables

Sample code:

<?php
$num1 = 123;
$num2 = "456";
$num3 = "789hello";
if (is_numeric($num1)) echo '$num1是数字';
if (is_numeric($num2)) echo '$num2是数字';
if (is_numeric($num3)) echo '$num3是数字';
?>

Output result:

$num1是数字
$num2是数字

Analysis:

We have defined three variables $num1, $num2 and $num3, where $num1 is an integer and $num2 and $num3 are numeric strings. By judging these three variables through the is_numeric() function, you can see that $num1 and $num2 are both recognized as numbers, and $num3 is judged as a non-numeric variable because it contains the non-numeric character "hello".

2. Check floating point variables

Sample code:

<?php
$num1 = 12.34;
$num2 = "56.78";
$num3 = "90.12hello";
if (is_numeric($num1)) echo '$num1是数字';
if (is_numeric($num2)) echo '$num2是数字';
if (is_numeric($num3)) echo '$num3是数字';
?>

Output result:

$num1是数字
$num2是数字

Analysis:

This time we defined three floating-point numeric variables $num1, $num2 and $num3, where $num1 and $num2 are floating-point numbers, and $num3 contains non-numeric characters. By judging these three variables through the is_numeric() function, you can see that $num1 and $num2 are both recognized as numbers, while $num3 is judged as a non-numeric variable.

3. Check other data type variables

Sample code:

<?php
$str1 = "Hello World";
$str2 = "1234";
$bool1 = true;
$arr1 = array('a', 'b', 'c');
if (is_numeric($str1)) echo '$str1是数字';
if (is_numeric($str2)) echo '$str2是数字';
if (is_numeric($bool1)) echo '$bool1是数字';
if (is_numeric($arr1)) echo '$arr1是数字';
?>

Output result:

$str2是数字

Parsing:

This time we defined four different data type variables $str1, $str2, $bool1 and $arr1. $str1 is a string type, $str2 is a numeric string type, $bool1 is a Boolean type, and $arr1 is an array type. Through the is_numeric() function to judge these four variables, you can see that only $str2 is judged to be a numeric type, and the other three variables are not numeric types.

Through these specific code examples, we can see how to use the is_numeric() function and the judgment rules. In actual PHP development, in many cases it is necessary to judge and verify the data type of variables. The is_numeric() function is a very convenient built-in function that can help us quickly judge the numeric type of variables.

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