编辑代码

<?php 
//行注释  #行注释
/*
块注释
*/
//值传递
$a=10;
$b=$a;
$b=5;
//echo $a,"\n",$b,"\n";

//引用传递
$c=10;
$d=&$c;
$c=5;
//echo $c,"\n",$d,"\n";

//常量
define('PI',3.14);
const PII=3;

//系统常量
echo PHP_VERSION,"\n",PHP_INT_SIZE,"\n",PHP_INT_MAX;