如何避免或忽視的檢索圖像，同時插入的phpmyadmin在PHP

Question

我新的PHP和我正在一個錯誤：

Could not retrieve image: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax

但我不想要檢索的形象，我想避免它。那麼，如何解決這個問題？

if(!isset($_SESSION["username"])) { 
    header("location:index.php"); 
} 

if(!empty($_SESSION['uid'])) { 
    $uidval = $_SESSION['uid']; 
} 

$uidval=""; 

if((isset($_GET['user_avatar'])) && (!empty($_GET['user_avatar']))) { 
    $user_avatar = $_GET['user_avatar'];  
} 

$getImage = mysqli_query($db, "SELECT user_avatar FROM user WHERE uid=" . $uidval) or die("Could not retrieve image: " .mysqli_error($db)); 

$path=mysqli_fetch_assoc($getImage) or die("Could not fetch array : " .mysqli_error($db)); 

Answer 1

有幾個錯誤：

1. $uidval="";必須高於if(!empty($_SESSION['uid'])) {...在 其他方式$uidval永遠是一個空字符串。
2. 如果$uidval爲空，那麼您必須跳過對數據庫的查詢。

實施例：

if(!empty($_SESSION["username"])) { 
    header("location:index.php"); 
    exit; 
} 


$uidval = !empty($_SESSION['uid']) ? $_SESSION['uid'] : ''; 

if(!empty($_GET['user_avatar'])) { 
    $user_avatar = $_GET['user_avatar'];  
} 

$path = ''; 
if (!empty($uidval)) { 
    $getImage = mysqli_query($db, "SELECT user_avatar FROM user WHERE uid=" . $uidval) or die("Could not retrieve image: " .mysqli_error($db)); 

    $path=mysqli_fetch_assoc($getImage) or die("Could not fetch array : " .mysqli_error($db)); 
}