PHP pi() Function

The pi() function returns the value of mathematical constant ? (pi). It returns a float value 3.14159265359 which is equal to the predefined constant M_PI in PHP.

Syntax

pi() : float

Parameters

This function requires no parameters.

Return Value

The pi() function returns the mathematical constant ? as a float value. This is equivalent to using the predefined constant M_PI, providing a convenient function-based alternative for mathematical calculations.

Example

Here's how to use the pi() function in mathematical calculations −

<?php
    echo "pi() = " . pi() . "<br>";
    echo "M_PI = " . M_PI . "<br>";
    echo "sqrt(pi) = " . sqrt(pi()) . "<br>";
    echo "M_SQRTPI = " . M_SQRTPI . "<br>";
    echo "2/sqrt(pi) = " . 2/sqrt(pi()) . "<br>";
    echo "M_2_SQRTPI = " . M_2_SQRTPI . "<br>";
    echo "Area of circle (radius=5): " . pi() * 5 * 5;
?>

The output of the above code is −

pi() = 3.1415926535898
M_PI = 3.1415926535898
sqrt(pi) = 1.7724538509055
M_SQRTPI = 1.7724538509055
2/sqrt(pi) = 1.1283791670955
M_2_SQRTPI = 1.1283791670955
Area of circle (radius=5): 78.539816339745

Conclusion

The pi() function provides a simple way to access the mathematical constant ? in PHP calculations. It's functionally identical to M_PI but offers a more readable function-based syntax for mathematical operations.