Mysql문의

<?php
include_once "**********";

$how = $_GET['how'];
$times = time();
$Bids = $_GET['Bids'];
$Sno = $_GET['Sno'];
$memoSno = $_GET['memoSno'];
$contents = $_GET['contents'];

print_r($_GET);

if($how == "reple"){
    $A = "INSERT INTO `alertmemo` (`memoSno`,`times`,`bid`,`sno`,`contents`) 
    VALUES (`".$memoSno."`,`".$times."`,`".$Bids."`,`".$Sno."`,`".$contents."`)";
    mysqli_query($conn,$A)or die(mysqli_error());
} // 답글에 댓글
else if($how == "edit"){
    
    
} // 수정
else if($how == "delete"){
    $A = "DELETE FROM alertmemo WHERE memoSno=`".$memoSno."`";
    mysqli_query($conn,$A);
    
    
} // 삭제
else if($how == "write"){
    $A = "INSERT INTO alertmemo ('contents','times','bid','sno','memoSno') VALUES ('".$contents."','".$times."','".$Bids."','".$Sno."','".$memoSno."')";
    
    mysqli_query($conn,$A);
    
    print mysqli_error($conn);
    
}  //댓글 작성

?>

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''contents','times','bid','sno','memoSno') VALUES ('test','1660806739','TNBreview' at line 1