<!--php嵌入HTML-->
<html>
<head>
<title>day01</title>
</head>
<body>
<h2>
<?php echo "Hello Php" ?>
</h2>
</body>
</html>
<?php
/*$声明变量并赋值*/
$a = 10;
$b = ‘Lemon‘;
$c = ‘柠檬‘;
$d = true;
$f = 55.55;
$key = $a;
$a=$b=$c=$d="value";
/* 显示数据类型
int:整型
sting：字符串
float :浮点型
一个汉字占3个字符长度*/
var_dump($a);
var_dump($b);
var_dump($c);
var_dump($d);
var_dump($f);
var_dump($key);
/*isset
* 检测当前数据是否被初始化
* 数据不定义不会分配内存空间*/
$num;
if(isset($num)){
echo"num被定义了";
}else{
echo"num没有被定义";
}
echo"<br>";
/*unset：释放变量*/
$num2 = 10;
unset($num2);
if(isset($num2)){
echo"num2被定义了";
}else{
echo"num2没有被定义";
}
echo"<br>";
/*empty
* 判断是否为空*/
$num3 = ‘ ‘;
if(empty($num3)){
echo"num3是空";
}else{
echo"num不是空";
}
/*变量名大小写敏感*/
$name = ‘zhangsan‘;
$NAME = ‘lisi‘;
echo$name;
echo"<br>";
echo$NAME;
echo"<br>";
/*单引号里面全是字符串
* 双引号可解析变量*/
$net = "lemon";
$age = 18;
/*双引号套单引号要加转移符*/
$string = "今天天气不错{$age}岁的{$net}出去\"玩\"了";
/*单引号套单引号要加转移符*/
$string2 = ‘今天天气不错{$age}岁的{$net}出\‘去\‘玩了‘;
echo$string;
echo"<br>";
echo$string2;
echo"<br>";
/*两种拼接字符串的方法*/
$string4 = ‘今天天气晴朗‘;
$string5 = ‘我们出去玩吧‘;
$result = "{$string4}{$string5}";
echo$result;
echo"<br>";
echo$string4.$string5;
原文：http://www.cnblogs.com/ningmeng666/p/6547582.html