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In website development, the user login module is an essential feature. Users may encounter input errors or server exceptions that cause login failure. Proper error handling and clear messages help users quickly fix issues and improve overall user experience. This article explains how to handle login errors in PHP and generate effective error messages.
User login errors mainly fall into two categories: user input errors and server-side errors.
User input errors mainly involve validating the form data submitted by users. We can use PHP conditional statements to check whether inputs are valid and output corresponding messages.
<?php
// Username and password validation
$username = $_POST['username'];
$password = $_POST['password'];
<p>if (empty($username)) {<br>
echo "Username cannot be empty";<br>
} elseif (empty($password)) {<br>
echo "Password cannot be empty";<br>
} elseif ($username != "admin" || $password != "123456") {<br>
echo "Username or password is incorrect";<br>
} else {<br>
echo "Login successful";<br>
// Other operations after successful login<br>
}<br>
?>
The code first obtains the username and password, checks whether the username is empty, then the password, next verifies whether the username and password match, and finally outputs the corresponding messages.
Server-side errors usually involve database connection failures or query exceptions. Using PHP’s error handling mechanism, we can catch these errors and output messages or write logs for later troubleshooting.
<?php
// Database connection
$servername = "localhost";
$username = "root";
$password = "password";
$dbname = "mydb";
<p>$conn = new mysqli($servername, $username, $password, $dbname);</p>
<p>if ($conn->connect_error) {<br>
die("Database connection failed: " . $conn->connect_error);<br>
}</p>
<p>// Database query<br>
$sql = "SELECT * FROM users";<br>
$result = $conn->query($sql);</p>
<p>if ($result->num_rows > 0) {<br>
// Process query results<br>
} else {<br>
echo "No users found";<br>
}</p>
<p>$conn->close();<br>
?>
The example attempts to connect to the database, outputs an error message if the connection fails. After executing the query, it checks if there are any results; if not, it outputs a message.
Handling user login errors is an important aspect of improving website stability and user experience. By using PHP’s conditional checks and error handling mechanisms, you can effectively catch user input issues and server exceptions, generating clear error messages that help users fix problems quickly and assist developers in troubleshooting. Designing reasonable error messages and logging mechanisms facilitates ongoing website optimization.
