Summary of PHP basic syntax
这篇文章主要介绍了PHP基本语法总结,本文从PHP能做什么开始讲解,对PHP的语法、注释、变量、常量等内容做了总结,需要的朋友可以参考下
一、PHP能做什么？
PHP能做什么？我觉得它很强大，只要我能想到的，它都能做，只是我技术能力还不行╮(╯﹏╰）╭。好吧，一张图，基本了解一下吧（ps:PHP的功能不局限于此( ^_^ )）
图像有点模糊，凑合一下，(≧▽≦)/
二、PHP语言标记
1、结束和开始标记
1.1 :属于xml风格，是PHP的标准风格，推荐使用。
1.2 :长风格标记，不常用。若你的奇葩编辑器不支持其他php标记，就用它吧
1.3 :简短风格，遵循SGML处理。需要在php.ini中将指令short_open_tag打开，或者在php编译时加入–enable-short-tags.如果你想你的程序移植性好，就抛弃这种风格，它就比1.1少了个php。
2、位置
怎么说呢？反正可以将PHP语言放在后缀名为.php的HTML文件的任何地方。注意了，是以.php结尾的HTML文件。
代码如下:
<html>
<html>
<head>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<!-- 在HTML标记中嵌入脚本 -->
<title><?php echo "PHP语言标记" ?></title>
</head>
<!-- 在属性位置嵌入 -->
<body <?php echo 'bgcolor="#ccc"'?>>
<!-- 来个高级点的吧 -->
<?php
if($exp){
?>
<!-- 属性值中嵌入php -->
<p align="<?php echo 'center'?>">条件为true该做的</p>
<?php
}else{
?>
<p>条件为FALSE该做的</p>
<?php
}
?>
</body>
</html>3、注释
3.1 单行注释：// 或者 # 多行注释：/* 说明*/
3.2 多行注释不能嵌套，但是其中可以包含单行注释；单行注释也可以包含多行注释。就想这样子
代码如下:
<?php
//echo "test";/*单行中包含多行注释符*/
/*echo 'test'; //多行注释符中包含单行注释符*/
?>三、变量
1、变量的使用
代码如下:
<?php
$a = 1; //声明一个变量a
$b = "php"; //声明一个变量b
$8d = 2; //非法变量名，只能以字母或者下划线开头且不包含空格
$i站点is = "php"; //合法变量名，可以使用中文
/*
*以下三个函数调用方式等效
*关键字和内置函数及用户自定义的类名，函数名不区分大小写
*/
phpinfo();
PhpInfo();
PHPINFO();
/*
*以下三个变量不一样
*变量名是区分大小写滴
*/
$name = "php1";
$Name = "php2";
$NAME = "php3";
//可变变量：变量名可以动态的设置
$hi = "hello";
$$hi = "world";
//以下均输出hello world
echo "$hi $hello";
echo "$hi ${$hi}";
//变量赋值
$foo = "B" //传值赋值
$bar = &$foo //引用赋值
$bar = "LZ";
echo "$foo"; //输出LZ
$cde = $foo; //传值赋值
$cde = "E";
echo "$foo"; //输出LZ
?>
2、变量的类型
四、常量
1、定义和使用
代码如下:
<?php
/*
*boolean define(string name,mixed value[,bool case_insensitive)
*name:常量名；value:常量值；第三个是个可选的布尔值，默认是FALSE（不区分大小写）
*/
define("FLO",1000);
echo FLO; //输出1000
//使用define函数检验FLO常量是否存在，存在则输出常量值
if(define("FLO"))
{
echo FLO;
}
?>2、常量和变量
2.1 常量的作用域是全局的，可以再脚本的任何地方声明和访问常量。
2.2 常量前面没有$,且不能通过赋值语句定义常量。
2.3 常量一旦被定义，不能被重新定义或取消定义，直到脚本运行结束自动释放。
2.4 常量的值只能是标量（boolean，integer,float,string中的一种类型)
3、系统的预定义常量
4、常用的魔术常量
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