PHP implements methods to obtain data in the database

<?php 
header("Content-type:text/html;charset=utf-8");//字符编码设置 
$servername = "localhost"; 
$username = "root"; 
$password = "root"; 
$dbname = "web"; 
 
// 创建连接 
$con =mysqli_connect($servername, $username, $password, $dbname); 
 
// 检测连接 
 
  
$sql = "SELECT * FROM users"; 
$result = mysqli_query($con,$sql); 
if (!$result) {
  printf("Error: %s\n", mysqli_error($con));
  exit();
}
 
$jarr = array();
while ($rows=mysqli_fetch_array($result,MYSQL_ASSOC)){
  $count=count($rows);//不能在循环语句中，由于每次删除 row数组长度都减小 
  for($i=0;$i<$count;$i++){ 
    unset($rows[$i]);//删除冗余数据 
  }
  array_push($jarr,$rows);
}
echo $str=json_encode($jarr);//将数组进行json编码
?>