To get the value of pi in php, the easiest way is use the php **pi()** function. **pi()** returns the value 3.1415926535898.

`echo pi(); // 3.1415926535898`

You can also use the php constant **M_PI**

`echo M_PI; // 3.1415926535898`

In php, we can easily get the value of pi for use in trigonometry with the php math functions.

For example, let’s say we want to find the sine of a number. The php sin() function takes a number in radians and then finds the sine of the number.

To find the sine of a number, we can use pi to make our lives easy.

To get the value of pi in your php code, you just call the **pi()** function as shown below.

`echo pi(); // 3.1415926535898`

Then, if you want to use it like in our example with finding the sine of a number, you can use the pi constant in the following way.

`echo sin(pi()/3); // 0.8660254037844386`

## pi Related Constants You Can Use in php

In php, you can also use the following constants to get the value of pi without using the php **pi()** function.

These constants are faster than calling the **pi()** function.

```
echo M_PI; // 3.14159265358979323846 pi
echo M_PI_2; // 1.57079632679489661923 pi/2
echo M_PI_4; // 0.78539816339744830962 pi/4
echo M_1_PI; // 0.31830988618379067154 1/pi
echo M_2_PI; // 0.63661977236758134308 2/pi
echo M_SQRTPI // 1.77245385090551602729 sqrt(pi)
echo M_2_SQRTPI // 1.12837916709551257390 2/sqrt(pi)
```

Hopefully this article has been helpful for you to understand how to find the value of pi in php.