The demo of json data returned by php is as follows. what causes this problem?

{Code...} php returns json data. if {code...} is contained in this line of code ajax, an error is returned. If this line of code is removed, the ajax result is successhtml code as follows: {code ...}

  query("select id from user2 where name = 'admin' and password ='admin'");//$user_details = $db->get_row(null, OBJECT, 0);//var_dump($user_details) ;$sql = sprintf("select * from user2 where name='%s' and password='%s'",$username,$password);//echo $sql;//select * from user2 where name='admin' and password='admin'$user=$db->get_results($sql);//var_dump($user);//array(1) { [0]=> object(stdClass)#5 (3) { ["id"]=> string(1) "1" ["name"]=> string(5) "admin" ["password"]=> string(5) "admin" } }if($user){  $result='0';   }else{   $result='-1';  }$arr = array ('a'=>1,'b'=>2,'c'=>3,'d'=>4,'e'=>5);echo json_encode($arr);?>

Php returns json data, if it contains

$user=$db->get_results($sql);  

This line of code ajax returns error.

If this line of code is removed, the ajax result is success.

The html code is as follows:

            
          
          
          
          
          
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