PHP basic case four: display student list

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1. Requirements Analysis

When we design the student information management system, Ability to query student information. After the administrator enters the student information interface, in order to easily add and delete student information, we will make the student data information visible in the table on the information interface.

2. Design ideas

1. How to define the basic information of students?

2. How to output the basic information of students in the form?

3. Knowledge reserve

1. Array

(1) What is an array?

An array is a collection of data that organizes a series of data to form an operable whole.

(2) How to define an array?

1) Use square brackets to wrap data

 $变量名 = [元素1,元素2,元素3];
 $info=['PHP中文网','PHP','数组'];

2) Use the array keyword (commonly used)

  $变量名 = array(元素1,元素2,元素3);
  $info=array('PHP中文网','PHP','数组');

3) Invisibly define the array: Add a square bracket to the variable, and the system will automatically turn it into an array

   ① $变量名[] = 值1;           //如果不提供下标也可以，系统自动生成数字下标（从0开始）；
 $info[]='PHP中文网';
    ②$变量名[下标] = 值;     //中括号里面的内容称之为下标 key，该下标可以是字母（单词）或者数字，与变量命名的规则相似
  $info[1]='PHP';

(3) Array type

1) Index array

The subscript (key name) of the index array ) consists of numbers, starting from 0 by default. Each number corresponds to the position of an array element in the array. There is no need to specify it. PHP will automatically assign an integer value to the key name of the index array, and then automatically increase from this value. As shown below:

$arr ​​= array(0=>'PHP Chinese website', 1=>'PHP tutorial', 2=>'PHP array', 3=>'http: //www.php.cn');

2) Associative array

The subscript (key name) of the associative array is composed of a mixture of numerical values ​​and strings. If there are If a key name is not a number, then the array is an associative array. As shown below:

$arr = array('title'=>'PHP中文网', 'course'=>'PHP 教程', 'content'=>'PHP 数组', 'url'=>'http://www.php.cn/course/php/');

3) Mixed array

$arr = array('title'=>'PHP中文网', 1=>'PHP 教程', 'content'=>'PHP 数组', 'http://www.php.cn/course/php/');

(4) Multidimensional array

1) Two-dimensional array:
All elements in the array are one Dimensional array;

2) Multi-dimensional array:
The array elements in the second dimension can continue to be arrays. There is no dimension limit in PHP
However, it is not recommended to use arrays with more than three dimensions. Increase access complexity and reduce access efficiency

3) Special-shaped array (irregular array):

The elements in the array are irregular, including ordinary variables and arrays

In the actual development process, it is not often used. Try to regularize the array elements for easy access

2. Loop statements

The common for loops in PHP include while, do...while, for and foreach.

For details, please see: https://www.w3school.com.cn/php/php_looping.asp.

3. Looping and array operations

1), use for loop to traverse the array
Syntax:

for($i=0;$i<conut($arr);$i++){
 //执行代码
 }

Note:
1 ) conut($arr); used to count the number of array elements.
2) The for loop can only be used to traverse the index array.
3) If there is an associative array, count will count the total number of the two arrays, and use a for loop to traverse the mixed array, causing the array to go out of bounds! !

2), foreach loop traverses the array
Syntax:

foreach($arr as $key=>$value){
 //执行代码
 }

or

foreach($arr as $value){
 //执行代码
 }

Note: foreach can traverse any type of array.

4. Code implementation

1. Define an array to save student information

$info = array(
       array('name'=>'王六','birth'=>'2003-08-07','subject'=>'PHP','snum'=>'0150427001'),
       array('name'=>'张三','birth'=>'2003-12-23','subject'=>'PHP','snum'=>'0150427002'),
       array('name'=>'赵二','birth'=>'2002-01-09','subject'=>'PHP','snum'=>'0150427003'),
       array('name'=>'孙四','birth'=>'2003-05-04','subject'=>'PHP','snum'=>'0150427004')
);

2. Use a for loop to display the student list

  <table>
              <tr><th>学号</th><th>姓名</th><th>出生日期</th><th>详情</th></tr>
              <?php for($i=0,$len=count($info);$i<$len;++$i){ ?>                 
              <tr>
                     <td><?php echo $info[$i][&#39;snum&#39;]; ?></td>
                     <td><?php echo $info[$i][&#39;name&#39;]; ?></td>
                     <td><?php echo $info[$i][&#39;birth&#39;]; ?></td>
                     <td><a href="#">点击查看详情</a></td>
              </tr>
              <?php } ?>
       </table>

5. Case display

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