(PHP 4, PHP 5, PHP 7)
pi — 锟矫碉拷圆锟斤拷锟斤拷值
锟斤拷锟斤拷圆锟斤拷锟绞的斤拷锟斤拷值锟斤拷锟斤拷锟斤拷值锟斤拷 float
锟斤拷锟斤拷锟斤拷锟斤拷 php.ini 锟叫碉拷 precision
指锟斤拷确锟斤拷锟斤拷默锟斤拷值锟斤拷 14锟斤拷锟斤拷也锟斤拷锟斤拷使锟斤拷
M_PI 锟斤拷锟斤拷锟斤拷锟矫筹拷锟斤拷锟斤拷锟斤拷锟斤拷 pi() 锟斤拷全锟斤拷同锟侥斤拷锟斤拷锟�
圆锟斤拷锟绞ｏ拷pi锟斤拷锟侥革拷锟斤拷锟斤拷锟街碉拷锟�
Example #1 pi() 锟斤拷锟斤拷
<?php
echo pi(); // 3.1415926535898
echo M_PI; // 3.1415926535898
?>