前面的话
PHP是一种创建动态交互性站点的强有力的服务器端脚本语言。PHP能够包含文本、HTML、CSS以及PHP代码，在服务器上执行，结果以纯文本返回浏览器
代码标识
PHP代码以结尾，且可以放置在文档中的任何位置
<span>php </span><span>// </span>?>
PHP语句以分号(;)结尾，PHP代码块的关闭标签也会自动表明分号
<span>php
echo </span><span>"</span><span>Hello World!</span><span>"</span><span>;
</span>?>注释
PHP支持三种注释，包括两种单行注释和一种多行注释
<span>php </span><span>//</span><span> 这是单行注释</span><span>#这也是单行注释 </span><span>/*</span><span>这是多行注释块 它横跨多行 </span><span>*/</span>?>
输出
在PHP中，有两种基本的输出方法：echo和print
print只能输出一个字符串，并始终返回1
echo能够输出一个以上的字符串，echo比print稍快，因为它不返回任何值
[注意]echo和print都是语言结构，有无括号都可以使用echo或echo()，以及print或print()，且echo或print关键字与字符串之间至少要有一个空格
<span>php
echo </span><span>"</span><span><h2>PHP is fun!</h2></span><span>"</span><span>;
echo </span><span>"</span><span>Hello world!<br></span><span>"</span><span>;
echo </span><span>"</span><span>I'm about to learn PHP!<br></span><span>"</span><span>;
echo </span><span>"</span><span>This</span><span>"</span>, <span>"</span><span> string</span><span>"</span>, <span>"</span><span> was</span><span>"</span>, <span>"</span><span> made</span><span>"</span>, <span>"</span><span> with multiple parameters.</span><span>"</span><span>;
</span>?><span>php
print </span><span>"</span><span><h2>PHP is fun!</h2></span><span>"</span><span>;
print </span><span>"</span><span>Hello world!<br></span><span>"</span><span>;
print </span><span>"</span><span>I'm about to learn PHP!<br></span><span>"</span><span>;
</span><span>//</span><span>该行出错，因为print只能输出1个字符串</span> print <span>"</span><span>This</span><span>"</span>, <span>"</span><span> string</span><span>"</span>, <span>"</span><span> was</span><span>"</span>, <span>"</span><span> made</span><span>"</span>, <span>"</span><span> with multiple parameters.</span><span>"</span><span>;
</span>?>计算表达式
不同于HTML和CSS，在PHP中可以写计算表达式
<span>php
</span><span>//</span><span>36</span> echo <span>12</span>*<span>3</span><span>;
</span>?>大小写
在PHP中，所有用户定义的函数、类和关键词都对大小写不敏感，但所有变量都对大小写敏感
<span>php
</span><span>//</span><span>Hello World!</span> ECHO <span>"</span><span>Hello World!<br></span><span>"</span><span>;
</span><span>//</span><span>Hello World!</span> echo <span>"</span><span>Hello World!<br></span><span>"</span><span>;
</span><span>//</span><span>Hello World!</span> EcHo <span>"</span><span>Hello World!<br></span><span>"</span><span>;
</span>?>[注意] .号代表字符串连接，在其他的编程语言中，一般用+号
<span>php
$color</span>=<span>"</span><span>red</span><span>"</span><span>;
</span><span>//</span><span>My car is red</span> echo <span>"</span><span>My car is </span><span>"</span> . $color . <span>"</span><span><br></span><span>"</span><span>;
</span><span>//</span><span>My house is </span> echo <span>"</span><span>My house is </span><span>"</span> . $COLOR . <span>"</span><span><br></span><span>"</span><span>;
</span><span>//</span><span>My boat is</span> echo <span>"</span><span>My boat is </span><span>"</span> . $coLOR . <span>"</span><span><br></span><span>"</span><span>;
</span>?>以上就介绍了前端学PHP之基础语法，包括了方面的内容，希望对PHP教程有兴趣的朋友有所帮助。
