PHP sqrt() Function

The sqrt() function returns the square root of a positive float number. Since square root for negative numbers is not defined, it returns NAN (Not a Number). This is one of the most commonly used mathematical functions in PHP.

This function always returns a floating point number.

Syntax

sqrt ( float $arg ) : float

Parameters

Return Values

PHP sqrt() function returns the square root of the given arg number. For negative numbers, the function returns NAN.

Examples

Basic Usage

Here's a basic example showing square root calculation −

<?php
    echo "sqrt(16) = " . sqrt(16) . "<br>";
    echo "sqrt(25) = " . sqrt(25) . "<br>";
    echo "sqrt(2) = " . sqrt(2) . "<br>";
?>

sqrt(16) = 4
sqrt(25) = 5
sqrt(2) = 1.4142135623731

Negative Number Example

When dealing with negative numbers, sqrt() returns NAN −

<?php
    echo "sqrt(-1) = " . sqrt(-1) . "<br>";
    echo "sqrt(-25) = " . sqrt(-25) . "<br>";
?>

sqrt(-1) = NAN
sqrt(-25) = NAN

Working with Variables

You can also use variables with the sqrt() function −

<?php
    $num1 = 64;
    $num2 = 100;
    
    echo "Square root of $num1 = " . sqrt($num1) . "<br>";
    echo "Square root of $num2 = " . sqrt($num2) . "<br>";
?>

Square root of 64 = 8
Square root of 100 = 10

Conclusion

The sqrt() function is essential for mathematical calculations in PHP. It works with positive numbers and returns NAN for negative values, making it reliable for basic square root operations.