PHP Variable Handling is_numeric() Function

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The PHP Variable Handling is_numeric() function is used to checks whether a value is a number or a numerical text.It is useful for checking if a variable includes a number. This function accepts both real numbers and numbers written in text.

For example, 123 and "123" are numerical, but "Hello" is not. If the input is a number or a numeric string, the function returns true. If the value is something else, it returns false. It is useful when working with numbers in programs. This function is available in PHP versions 4, 5, 7, and 8.

Syntax

Below is the syntax of the PHP Variable Handling is_numeric() function −

bool is_numeric ( mixed $value )

Parameters

This function accepts $value parameter which is the value to see if it is a number or a numeric string.

Return Value

The is_numeric() function returns TRUE if the value is a number or a numeric string. And it returns FALSE if the value is not a number.

PHP Version

First introduced in core PHP 4, the is_numeric() function continues to function easily in PHP 5, PHP 7, and PHP 8.

Example 1

This program uses the PHP Variable Handling is_numeric() function to find out whether or not different values are numeric. It checks three types of strings: numbers, numerical strings, and non-numerical strings. It is useful to understand how is_numeric() works.

<?php
   // Integer   
   $val1 = 123;      
   // Numeric string   
   $val2 = "456";    
   // Non-numeric string   
   $val3 = "Hello";  

   echo is_numeric($val1) ? "True\n" : "False\n";  
   echo is_numeric($val2) ? "True\n" : "False\n";  
   echo is_numeric($val3) ? "True\n" : "False\n";  
?>

Output

Here is the outcome of the following code −

True
True
False

Example 2

In the below PHP code we will use the is_numeric() function and check the function on different types of data formats. It compares floats, negative numbers, and Boolean values.

<?php
   // Float
   $val1 = 3.14;     
   // Negative integer
   $val2 = -500;     
   // Boolean
   $val3 = true;     

   echo is_numeric($val1) ? "True\n" : "False\n";  
   echo is_numeric($val2) ? "True\n" : "False\n";  
   echo is_numeric($val3) ? "True\n" : "False\n";  
?> 

Output

This will generate the below output −

True
True
False

Example 3

Now the below code checks if user input is numeric or not using the is_numeric() function. It makes sure that user enters a number before performing calculations. This is useful for form validation in PHP.

<?php
   $user_input = "1000";  

   if (is_numeric($user_input)) {
      echo "Valid number: $user_input\n";
   } else {
      echo "Invalid input. Please enter a number.\n";
   }
?> 

Output

This will create the below output −

Valid number: 1000

Example 4

The program defines a function to identify whether a value is numeric. It helps to check multiple inputs before processing. Useful in real-world scenarios, such as data validation.

<?php
   function checkValue($value) {
      if (is_numeric($value)) {
         return "Valid number: $value\n";
      } else {
         return "Invalid input. Not a number.\n";
      }
   }

   echo checkValue(500);       
   echo checkValue("45.67");   
   echo checkValue("ABC"); 
?> 

Output

Following is the output of the above code −

Valid number: 500
Valid number: 45.67
Invalid input. Not a number.