[学习交流] 常量

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<?php
//定义形式1
define("PI", 3.1415926);
define("SCHOOL", "传智播客");
define("CC1", 1234);
define("CC2", "abcd");
//定义形式2
//const CC1 = 1234;
//const CC2 = 'abcd';
//使用形式1
echo " 常量PI的值是：".PI;
echo " 常量SCHOOL的值是：".SCHOOL;
$s1 = PI*3*3;
//使用形式2：使用函数constant（）获得常量的值
$s2 = constant("PI")*3*3;
echo " s1=$s1,s2=$s2";
echo " ".SCHOOL.constant("CC1").constant("CC2");
//取得常量值的灵活语法//常量的名字也可以拼凑
$i=1;
$c1="CC".$i;
echo " 常量$c1的值为：".constant($c1);
echo " ";
//判断常量是否存着
if(defined("PI")){
echo"PI is cunzai";//常量存着
}else{
echo "PI is bucunzai";
define("PI",3.1415926);//常量不存在创建常量
}
$s3=PI*5*5;
echo " mianji=$s3";
echo " ";
if(defined("G")){
echo"G is cunzai";//常量G存着
}else{
echo "G is bucunzai";
define("G",9.8);//常量G不存在创建常量
}
$s4=G*5;//G为重力加速度
echo " shudu：$s4";
echo " ";
echo "v2 de zhi wei".$v2;
echo " ";
echo "C1 de zhi wei".C1;
echo " ";
echo CC1;
echo " ";
//预定义常量
echo M_PI;
echo " ";
echo PHP_os;
echo " ";
echo PHP_VERSION;
echo " ";
//魔术常量
echo " ".__FILE__;//当前网页文件的完整物理路径
echo " ". __DIR__;
echo " ".__LINE__;//当前常量所在的行号
echo " ".__LINE__;
?>
<?php
$n1=123;
$s1=decbin($n1);
$s2=decoct($n1);
$s3=dechex($n1);
echo " $s1";
echo " $s2";
echo " $s3";
$n4=0123;
$n5="0123";
$n6="123";
$n7=0x12;//其实就是$n7=18;or $n7="18";or $n7="0x18";
$n8="0x12";
$n9="12";
$n10=12;
$s7=hexdec($n7);
$s8=hexdec($n8);
$s9=hexdec($n9);
$s10=hexdec($n10);
echo " $s7";//24
echo " $s8";//18
echo " $s9";//18
echo " $s10";//18
$s11=dechex($n7);
echo " $s11";//12
echo " $n4, $n7";//83,18
echo " php的输出结果是：".(8.1/3);
?>
<script>
document.write(" js的输出结果是："+(8.1/3));
</script>
<?php
echo " ";
if(!empty($_POST)){
$d1=$_POST['data1'];
$d2=$_POST['data2'];
$n1=$_POST['num1'];
$n2=$_POST['num2'];
$n3=$_POST['yunsuanfu'];
echo "d1=$d1,d2=$d2,n1=$n1,n3=$n3,n2=$n2";
If($n3=="+"){$jieguo=$n1 + $n2;
}else if ($n3=="-"){
$jieguo=$n1 - $n2;
}else if ($n3=="*"){
$jieguo=$n1 * $n2;
}else if ($n3=="/"){
$jieguo=$n1 / $n2;
}
echo"jieguo=$jieguo,<hr/r>";
print_r($_POST);
}else{echo"非法的页面访问";
$jieguo="";
$n1="";
$n2="";
}
?>

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[学习交流] 常量

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