Question

$dbhost = 'localhost';
$dbuser = 'root';
$dbpass = '';
$db = 'blood_db';


$connection = new mysqli($dbhost,$dbuser,$dbpass,$db);

if($connection->connect_error){
    die("Server Error ".$connection->connect_error);
}
else{

    $query = ("SELECT first_name FROM accounts WHERE email_address = '".$_SESSION['username']."'");

    $obj = $connection->query($query);

    echo "Welcome ".$obj->first_name;

这里显示了一个通知，即＆＃34; 注意：未定义的属性：mysqli_result :: $ first_name＆＃34; 它正在返回对象，那么如何从中提取名字呢？

// printf("Welcome %s",$result->);
echo '<br><a href="logout.php">Logout</a>';

Answer 1

使用下面的代码

  $result = $connection->query($query);
  if($result){
      $row = $result->fetch_assoc();
     echo "Welcome ".$row['first_name'];
  }else{
      // check error 
  }

Answer 2

如果要检查数据是否为空，您可以尝试选择数据并添加条件

$obj = $connection->query($query);
if ($obj->num_rows > 0) {

    $row = $obj->fetch_assoc();
    echo "Welcome ".$row['first_name'];
}

如果您不想检查数据，请使用此

 $row = $obj->fetch_assoc();
 echo "Welcome ".$row['first_name'];

了解更多信息

https://www.w3schools.com/php/php_mysql_select.asp

Answer 3

一个非常基本的例子是这样的：

<?php

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test";
$firstname = "";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 

$sql = "SELECT * FROM tbl_test WHERE email_address = '". $_SESSION['username']. "'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // Retrieve Firstname
    while($row = $result->fetch_assoc()) {
        $firstname = $row["first_name"];
    }
} else {
    echo "No results found!";
}
?>

<!DOCTYPE html>
<html>
<head>
    <title>Test</title>
</head>
<body>
    <header>
        <h3>Welcome <?php echo $firstname; ?></h3>
    </header>
</body>
</html>

<?php
$conn->close();


?>

在html页面上显示从数据库中检索的名字的最佳方法是什么？

3 个答案: