Some basic syntax of php

1.php tag

  <?php
     echo &#39;Hello&#39;;
  ?>

2.Constant

constTHE_VALUE = 100;
       define('THE_VALUE',100);
  变量 $a=10;

3.Function

  functiontraceHello($name){
       echo &#39;hello &#39;.$name.&#39;<br>&#39;;//字符串连接
       //echo "hello $name <br>";
       return 1;//返回值
    }
 
    调用：
       1.traceHello(&#39;zhangsan&#39;);
       2.$func=&#39;traceHello&#39;
         $func(&#39;zhangsan&#39;);

4. Process control

  1.if else
        function getLevel($score){
            if($score>=90){
                 return'优秀';
            }elseif($score>=80){
                 return '良好';
            }else{
                  return '不好';
            }
          }
      2.switch
         function getLevel($score){
              $result = '不好';
              switch(intval($score/10)){//intval()取整或取出其中整数
                 case 10:
                 case  9:
                      $result = '优秀';
                      break;
                 case  8:
                      $result = '良好';
                      break;
                 default:
                      $result = '不好';
                      //break;
               }
              return $result;
          }

3.for loop

 for($i=0;$i<100;$i++){
             if($i==20){ break; }
             if($i==40){ continue; }
          }
       4.while循环
           $i=0;
           while(%<10)
              ...
              $i++;
           }
       5.do while循环
          $i=0;
          do{
              ...
              $i++;
           }while($i<100);

5. Logical operators

|| && !

6. Common methods for strings

   strpos($str,'o');
   substr($str,2);
   str_split();
   explode(' ',$str);

7. Array

$arr=array();
   $arr[0]='Hello';
   print_r($arr);
 
   $arr['h']='hello';
   $arr['w']='world';
 
   $arr =array('h'=>'hello','w'=>'world')

8.

require 'lib.php';//依赖，文件不存在报错
  require_once 'lib.php';//只引用一次
  include 'lib.php';//包含，文件不存在给出警告

9. Declare class

   namespace jk;//命名空间
     class Man{
       private $_age,$_name;
       private static $NUM = 0;//静态变量
       
        /**
        * @param int $age 年龄
        * @param string $name 名字
       public funcation _construct($age,$name){
          $this-> _age = $age;//this当前对象指针，self当前类指针，parent父类指针
          $this-> _name = $name;
       }//构造方法
       public funcation sayHello(){}//成员方法
       public static funcation say(){}//类方法
     }
  创建实例
     $a=new Man();
    $a->sayHello();//调用方法
     Man::say();
 
     $h = new\jk\Hello();//存在命名空间

10. Class inheritance, override method

class Child extends Man{
       publicfunction _construct($age,$name){
         parent::_contruct($age,$name);
       }
      
       publicfunciton say(){//重写方法
         //parent::say(); //保留父类方法
         echo 'child';
       }
    }

11. Commonly used library functions

time();//时间戳
  date_default_timezone_set('Asia/Shanghai');//时区设置
   date('Y-m-d H:i:s');//时间
   date('Y-m-d H:i:s'，time());//时间戳转换成时间
 
   $obj =array('h'=>'Hello','w'=>'World');
   echo json_encode($obj);//转换成json格式
   $jsonStr ='{"h":"Hello","w":"World"}';
   $obj =json_decode($jsonStr);//json字符串转换为php对象
 
   $f = @fopen('data','w');//打开文件,@不输出警告
   fwrite($f,'hello');//写入文件
   fclose($f);
   $f = @fopen('data','r');
   while(!feof($)){//判断是否到达文件尾
      $content =fgets($f);//只能读取一行
      echo$content;
   }
   echofile_get_contents('data');//直接获取文件
 
   die('结束页面');

12. Get get parameters and post parameters

 if(isset($_GET['name'])&& $_GET['name']){}//isset()判断变量是否设置empty($name)判断变量是否赋值

13. Get files

  $file = $_FILES['file'];
   $fileName = $file['name'];
  move_uploaded_file($file['tmp_name'],$fileName);

14.

cookie和session
   setcookie('name','cheng');
   header('Location:a.php');//跳转
 
    //a.php
    echo $_COOKIE['name'];//获取cookie
 
    session_start();//启用session
    $_SESSION['name'] ='cheng';
    echo session_id();//获取sessionid
    echo$_SESSION['name'];//
    session_destroy();//销毁session

15.mysql database

  $conn =mysql_connect('localhost','root','password');
   mysql_select_db('mydb',$conn);
    $result =mysql_query("SELECT * FROM users");//查询，或更新，或删除
    $result_arr =mysql_fetch_array($result);//一次取一条，以数组形式，有索引
    $result_arr =mysql_fetch_assoc($result);//不含索引
    $data_count =mysql_num_rows($result);//获取数据条数
 
    if(mysql_errno()){
       echomysql_error();//获取错误
    }

16.PDO

php data object provides a database access abstraction layer. No matter which database is used, the same method is used.

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