The is_numeric() function in PHP is used to determine whether a given variable is a number or a numeric string. It checks if the value can be interpreted as a number, either as an integer, float, or a numeric string.

Syntax:

is_numeric($value)

Parameters:

• $value: The variable or value you want to check.

Return Value:

• true if the value is numeric (can be interpreted as a number).
• false if the value is not numeric.

Example 1: Checking Numeric Values

<?php
// Numeric values
var_dump(is_numeric(123));          // true (integer)
var_dump(is_numeric(123.45));       // true (float)
var_dump(is_numeric('123'));        // true (numeric string)
var_dump(is_numeric('123.45'));     // true (numeric string)
?>

Output:

bool(true)
bool(true)
bool(true)
bool(true)

Example 2: Non-numeric Values

<?php
// Non-numeric values
var_dump(is_numeric('Hello'));      // false (non-numeric string)
var_dump(is_numeric('123abc'));     // false (alphanumeric string)
var_dump(is_numeric(array()));      // false (array)
var_dump(is_numeric(null));         // false (null)
?>

Output:

bool(false)
bool(false)
bool(false)
bool(false)

Example 3: Scientific Notation and Hexadecimal

<?php
// Scientific notation
var_dump(is_numeric('1.2e3'));      // true (scientific notation, equivalent to 1.2 * 10^3)

// Hexadecimal value (not numeric)
var_dump(is_numeric('0x1A'));       // false (hexadecimal string, not considered numeric)
?>

Output:

bool(true)
bool(false)

Practical Usage:

• is_numeric() is useful when you need to validate user input or check if a value can be used in mathematical operations.
• It helps ensure that variables are valid numbers before performing calculations to avoid errors or unexpected behavior.

Summary:

• is_numeric() checks whether a value is a valid number or numeric string.
• It returns true for integers, floats, and numeric strings, and false for non-numeric values.