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PHP容易忘记的知识点分享

Jun 13, 2016 am 11:53 AM
definephpcodesharecopydefinitionconstantKnowledge points

1、定义常量:

复制代码 代码如下:


//1
define("TAX_RATE",0.08);
echo TAX_RATE; //输出0.08
//2 (PHP 5.3)
const TAX_RATE2 =0.01;
echo '--'.TAX_RATE2; //输出0.01
?>



2、require 和require_once 区别:

前者遇到即包含文件,后者会判断是否已经包含过了,如果包含过了,则不再包含文件。一可以节省资源,二可以避免重复定义的错误。

3、include 和include_once的区别:

作用和功能都可以把一个页面,包含到另外一个页面,前者可以包含多次,后者只包含一次。

4、include 和require 区别(同时include_once 和 require_once)

相同:都是可以引入别的页面

不同:include 如果出现了错误,会继续执行,require 出现错误,则会终止程序。

结论:在做项目的时候 基本上使用 require_once 并且写在PHP最前面。

5、PHP中 定义变量区分大小写,定义函数的时候不区分大小写

复制代码 代码如下:


/* 定义变量区分大小写*/
$abc=100;
$Abc=200;
echo $abc.'|'.$Abc; //输出100|200
/*定义函数不区分大小写 下面写法系统会报错:Fatal error: Cannot redeclare Abc() */
function abc(){
echo 'abc';
}
function Abc(){
echo "Abc";
}
?>



6、在mysql安装的时候设置字符集为UTF-8,而在mysql客户端(cmd进入的界面)向表中添加中文的数据 无法添加到数据库中,则按下面设置即可:

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