PHP 常用功能

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1.PHP 字符串

<?php/*字符串分割*/$str = 'Hello php';//''or ""//echo $str;//Hello php//输出ll在字符串的位置,第一个//echo strpos($str,"l");//2$str1 = substr($str,2,3);//截取字符串str,从2开始,截取长度为3,不写第三个项则截至最后//echo $str1;//llo$result = str_split($str);//分割字符串,默认1个1段//echo $result;//错误,无法输出数组//print_r($result);//Array ( [0] => H [1] => e [2] => l [3] => l [4] => o [5] => [6] => p [7] => h [8] => p )$result2 = str_split($str,2);//2个1段//print_r($result2);//Array ( [0] => He [1] => ll [2] => o [3] => ph [4] => p )$str = $str." JAVA C# C++";//echo $str;//Hello php JAVA C# C++$result3 = explode(" ",$str);//按空格进行分割//print_r($result3);//Array ( [0] => Hello [1] => php [2] => JAVA [3] => C# [4] => C++ )/*字符串连接*/$num = 100;$str2 = $str.'<br>Objective-C'.$num;//echo $str2;//Hello php JAVA C# C++            //Objective-C100$str2 = "$str<br>Objective-C $num";//另一写法,用""echo $str2;//结果同上

2.PHP数组

<?php$arr = array();$arr[0] = "HELLO";$arr[1] = "WORLD";$arr[2] = 3.1415926;//print_r($arr);//Array ( [0] => HELLO [1] => WORLD [2] => 3.1415926)for($i = 0;$i<100;$i++){    array_push($arr,"添加的元素$i");//添加}//print_r($arr);$arr2 = array();$arr2['h'] = 'hello';//键值对$arr2['m'] = 'mm';//print_r($arr2);//Array ( [h] => hello [m] => mm )//echo $arr2['m'];//mm$arr3 = array(0=>'mm','c' =>'初始化','h'=>'hello');//数组初始化//print_r($arr3);//Array ( [0] => mm [c] => 初始化 [h] => hello )echo $arr3[0].$arr3['h'];//mmhello

3.include与require

先定义3个php文件:

lib.php

<?phpfunction sayHello(){    echo 'HELLO PHP';}

lib2.php

<?phpfunction sayHello(){    echo 'HELLO PHP';}echo "This is a lib file";

lib3.php

<?phpecho "This is a lib file";

主文件:

<?php/*//sayHello();//未定义,错误require 'lib.php';//也可用include//sayHello();//HELLO PHP//已知m.php不存在include 'm.php';//warning  包含require 'm.php';//error  依赖//二者功能相同,只是错误提示的级别不同*//*require 'lib2.php';require 'lib2.php';//ERROE,引入2次,sayHello被定义2次sayHello();*//*require 'lib3.php';require 'lib3.php';//输出了2次:   This is a lib fileThis is a lib file*/require_once 'lib3.php';require_once 'lib3.php';include_once 'lib3.php';//总共只执行1次: This is a lib file//require_once 和 include_once 一样,先检查前面是否调用了,没有才调

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