The sqrt() function in PHP is used to calculate the square root of a number. It returns the positive square root of the given number. If the input is negative, sqrt() will return NAN (Not A Number).

Syntax:

sqrt($number);

• $number: The number for which you want to calculate the square root. It must be a positive number or zero.

Examples:

Example 1: Square root of a positive number

<?php
$number = 16;
$result = sqrt($number);
echo "The square root of $number is $result.";
?>

Output:

The square root of 16 is 4.

Example 2: Square root of zero

<?php
$number = 0;
$result = sqrt($number);
echo "The square root of $number is $result.";
?>

Output:

The square root of 0 is 0.

Example 3: Square root of a negative number

<?php
$number = -9;
$result = sqrt($number);
echo "The square root of $number is $result.";
?>

Output:

The square root of -9 is NAN.

(Note: You can check for NAN by using is_nan().)

Example 4: Square root of a decimal number

<?php
$number = 2.25;
$result = sqrt($number);
echo "The square root of $number is $result.";
?>

Output:

The square root of 2.25 is 1.5.

Handling NAN:

You can use is_nan() to check if the result is NAN.

<?php
$number = -25;
$result = sqrt($number);
if (is_nan($result)) {
    echo "The square root of $number is not a number.";
} else {
    echo "The square root of $number is $result.";
}
?>

Output:

The square root of -25 is not a number.

This should cover the basics of using the sqrt() function in PHP!