预期参数错误php [重复]

Question

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I get this error when I upload it on hosting server but the site is good when in localhost, php version setting is in 7.1.

Warning: mysqli_query() expects at least 2 parameters, 1 given in /storage/ssd3/410/5444410/public_html/update.php on line 42

Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, null given in /storage/ssd3/410/5444410/public_html/update.php on line 43

Code:

<?php 
    $conn_db = mysqli_connect("localhost","user","password") or die();
    $sel_db = mysqli_select_db($conn_db, "dbname") or die();
    if(isset($_POST['update_password']))
    {
    $old_password=$_POST['old_password'];
    $new_password=$_POST['new_password'];
    $confirm_password=$_POST['confirm_password'];
    $chg_pwd=mysqli_query("SELECT * from member WHERE username='$user_check'"); //line 42
    $chg_pwd1=mysqli_fetch_array($chg_pwd); //line 43
    $data_pwd=$chg_pwd1['password'];
    if($data_pwd==$old_password){
    if($new_password==$confirm_password){
        $update_password=mysqli_query("UPDATE member SET password='$new_password' WHERE username='$user_check'");
        $viewpass = 'UPDATED SUCCESSFULLY!';
    }
    else{
        $errMsg = 'PASSWORD DOES NOT MATCH!';
    }
    }
    else
    {
    $errMsg2 = 'OLD PASSWORD IS WRONG!';
    }}
?>

I'm just making a simple photo portfolio site, I don't know what to do with this.

</div>

Answer 1

Try this

$chg_pwd=mysqli_query($conn_db,"SELECT * from member WHERE username='$user_check'"); 
$chg_pwd1=mysqli_fetch_array($chg_pwd, MYSQLI_ASSOC); 

for associative array, or

$chg_pwd1=mysqli_fetch_array($chg_pwd, MYSQLI_NUM); 

for numeric array.