PHP, mysqli implementation of simple Add, delete, change, check function (beginner)

<title>index.php</title><?php      #连接数据库      $conn  = mysqli_connect ("localhost", "root", "");         #判断是否连接成功     if (! $conn) {        echo  "failed";     }        //Select Database     mysqli_select_db ($ Conn, "BBS");         //preparing SQL statements      $sql  =  "Select * from bbs_user";         //Send SQL statements       $obj  = mysqli_query ($conn, $sql);         echo   "<center>";    echo  "<table border = 1 cellspacing  =  ' 0 '  cellpadding =  ' >;    echo  ' <th> ref. &LT;/TH ><th> name &Lt;/th><th> Password </th><th> Address </th><th> gender </th><th> age </th><th > Operation </th> ";     while ($row  = mysqli_fetch_assoc ($obj)) {         echo  "<tr>";             echo  ' <td> '. $row [' id ']. ' </td> ';            echo  ' <td> '. $ row[' username ']. ' </td> ';            echo  ' <td> '. $ row[' password ']. ' </td> ';            echo  ' <td> '. $ row[' address ']. ' </td> ';            echo  ' <td> '. $ row[' sex ']. ' </td> ';            echo  ' <td> '. $ Row[' age ']. ' </TD> ';            echo  ' <td><a  href =  "del.php?id=". $row [' id ']. ' " > Delete </a>/<a href =  "update.php?id=". $row [' id ']. ' " > Modify </a></td> ';        echo  ' </tr> ';     }        echo  "</table>";     echo  "<a href =  ' add.php ' > Add </a>";     echo   "<center>";         //close Connection     mysqli_ Close ($conn);? >

Click Delete:

<title>del.php</title><?php $id =$_get[' id '];    $link = Mysqli_connect (' localhost ', ' root ', ');    if (! $link) {exit (' connection failed ');    } mysqli_select_db ($link, ' BBS ');    $sql = "Delete from Bbs_user where id = $id";    $result = Mysqli_query ($link, $sql);    if ($result && mysqli_affected_rows ($link)) {echo "delete succeeded <a href = ' index.php ' > Return </a>";    }else{echo "Delete failed"; } mysqli_close ($link);? >

Change data:

<?php     $id  = $_get[' id '];        $ Link = mysqli_connect (' localhost ', ' root ', ');     if (! $link) {         exit (' connection failed ');    }         mysqli_select_db ($link, ' BBS ');     $sql  =  "Select * from bbs _user where id = $id ";     $obj  = mysqli_query ($link, $sql);      $row  = mysqli_fetch_assoc ($obj);? ><form action= "doupdate.php?" >    <!--use hidden to get ID, other currently not-->    <input type= "hidden"  name= "id"  value =  "<?php echo  $id;? > " />    <table border = 0 cellpadding="   cellspacing= "0" >        <tr><td> number:</td><td><?php echo  $row [' id '];? ></td></tr>        <tr><td> User name:</td> <td><input type= "text"  name =  "username"  value= "<?php echo  $row [' username '];? > " /></td></tr>        <!--<tr><td > Password: </td><td><input type= "text"  name =  "password"  value= "<?php  echo  $row [' Password '];? > "&NBSP;/&GT;&LT;/TD&GT;&LT;/TR&GT;--&GT;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&LT;TR&GT;&LT;TD > Password:</td><td><?php echo  $row [' Password '];? ></td></tr>        <tr><td> Address:</td> <td><input type= "text"  name= "Address"  value= "<?php echo  $row [' address '];? > " /></td></tr>        <tr><td> Sex: </td><td><input type= "text " name=" Sex " value=" <?php echo  $row [' sex '];? > " /></td></tr>        <tr><td> Age: </td><td><input type= "Text"  name= "Age"  value= "<?php echo  $row [' Age ' ];? > " /><br />        <tr><td colspan = "2"  align= "center" ><input type= "submit"  name= " value=" Commit " /></td> </tr>    </table></form>

Execute changes:

<?php      $id  = $_get[' id '];     $username  =  $_get[' username '];    # $password  = $_get[' password '];      $address  = $_get[' address '];     $sex  = $_get[' sex '];      $age  = $_get[' age '];          $link  =  mysqli_connect (' localhost ', ' root ', ');     if (! $link) {         exit (' connection failed ');     }        mysqli _select_db ($link, ' BBS ');     $sql  =  "Update bbs_user set username  =  ' $username ', address =  ' $address ', sex =  ' $sex ',  age =   ' $age '  where id = $id ";     $obj  = mysqli_query ($link, $sql);     iF ($obj  && mysqli_affected_rows ($link)) {        echo   "Modify success <a href =  ' index.php ' > Return </a>";    }else{         echo  "Modify Failed";    }         mysqli_close ($link);    ?>

Add Data:

<form action =  ' doadd.php '  method= ' get ' >      ID: <input type= "text"  name= "id"  value= ""/><br />      Name: <input type= "text"  name= "username"  value= ""/><br />      Password: <input type= "text"  name= "password"  value= ""/><br />      Address: <input type= "text"  name= "Address"  value= ""/><br />      Sex: <input type= "Radio"  name= "Sex"  value =  "male"/> Male           <input type= "Radio"  name= "Sex"  value= "women"  /> women < br />    : <input type= "text"  name= "Age"  value= ""/><br  />    <input type= "Submit"  value= "Submission" &NBSP;/></FORM> 

To perform the Add data:

<?php     //get added data information      $id  = $_get[' id '];      $username  = $_get[' username '];     $password  = md5 ($_ get[' password ');//encryption      $address  = $_get[' address '];    $ sex = $_get[' sex '];     $age  = $_get[' age '];    // Connect to Database      $link  = mysqli_connect (' localhost '  ,  ' root '  ,  ');         //determine if the connection succeeds     if (! $link) {         exit (' Connection database failed '. Mysqli_connect_error ());    }         //Select Database     mysqli_select_db ($link  ,  ' BBS ');         //preparing SQL statements      $sql  =  " Insert into bbs_user (iD,username,password,address,sex,age)  values (' $id ', ' $username ', ' $password ', ' $address ', ' $sex ', ' $age ');         //Sending SQL statements      $obj  = mysqli_query ($link  ,  $sql);         if ($obj) {         echo  Add success <a href =  ' index.php ' > Return </a> ';     }else{        echo  "Add failed";     }     mysqli_close ($link);? >

PHP, mysqli implementation of simple Add, delete, change, check function (beginner)