PHP sqrt() Function

Definition and Usage

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

This function always returns a floating point number.

Syntax

sqrt ( float $arg ) : float

Parameters

Return Values

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

PHP Version

This function is available in PHP versions 4.x, PHP 5.x as well as PHP 7.x.

Example

Following example calculate square root of 100−

<?php
   $arg = 100;
   echo "Square root of " . $arg . "=" . sqrt($arg) . "\n";
?>

Output

This will produce following result −

Square root of 100=10

Example

For sqrt(2), 1/sqrt(2) and sqrt(3), PHP has special predefined constants M_SQRT2, M_SQRT1_2 and M_SQRT3 respectively −

<?php
   echo "sqrt(2) = " . sqrt(2) . "\n";
   echo "M_SQRT2 = " . M_SQRT2. "\n";
   echo "sqrt(3) = " . sqrt(3) . "\n";
   echo "M_SQRT3 = " . M_SQRT3 . "\n";
   echo "1/sqrt(2)) = " . 1/sqrt(2) . "\n";
   echo "M_SQRT1_2 = " . M_SQRT1_2 . "\n";
?>

Output

This will produce following result −

sqrt(2) = 1.4142135623731
M_SQRT2 = 1.4142135623731
sqrt(3) = 1.7320508075689
M_SQRT3 = 1.7320508075689
1/sqrt(2)) = 0.70710678118655
M_SQRT1_2 = 0.70710678118655

Example

The mathematical constants M_SQRTPI and M_2_SQRTPI represent values of sqrt(Π) and 2/sqrt(Π) −

<?php
   echo "sqrt(pi) = " . sqrt(M_PI) . "\n";
   echo "M_SQRTPI = " . M_SQRTPI. "\n";
   echo "2/sqrt(pi) = " . 2/sqrt(M_PI) . "\n";
   echo "M_2_SQRTPI = " . M_2_SQRTPI . "\n";
?>

Output

This will produce following result −

sqrt(pi) = 1.7724538509055
M_SQRTPI = 1.7724538509055
2/sqrt(pi) = 1.1283791670955
M_2_SQRTPI = 1.1283791670955

Example

sqrt(-1) is undefined hence it returns NAN

<?php
   echo "sqrt(-1) = " . sqrt(-1) . "\n";
?>

Output

This will produce following result −

sqrt(-1) = NAN