The irrational mathematical constant of Pi can be obtained a few different ways in PHP. There is a function to give you the value as well as a bunch of constants that represent Pi as well as fractions of Pi and it’s square root. Heck, you could even do it the old fashioned way:

``````\$pi = 245850922 / 78256779;
``````

But that doesn’t make much sense when there’s so many built-ins. To obtain the value of Pi with PHP’s built in function is easy (and logically named ;):

``````\$pi = pi();
``````

But why use a function when you could simply reference a constant? I mean, Pi is a constant already, so for me this makes the most sense:

``````\$pi = M_PI;
``````

Then for fractions and square roots of pi we can utilize these:

``````\$half_pi          = M_PI_2;
\$quarter_pi       = M_PI_4
\$one_over_pi      = M_1_PI;
\$two_over_pi      = M_2_PI;
\$sqrt_pi          = M_SQRTPI;
\$two_over_sqrt_pi = M_2_SQRTPI;
``````

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