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In PHP programming, database connection is a very basic and important step, and is usually implemented using connect() functions (such as mysqli_connect() or PDO connection methods). The correct username and password are one of the key factors in successfully establishing a connection. If the username or password is spelled incorrectly, a connection failure is an inevitable result. This article will explain the reasons behind it in detail and use PHP code examples to illustrate it.
When connecting to a database using the connect() function, you usually need to provide the following information:
Host address (host)
Username
Password
Database name (database)
For example, the basic form of using the mysqli_connect() function is as follows:
$connection = mysqli_connect("m66.net", "username", "password", "database");
if (!$connection) {
die("Connection failed: " . mysqli_connect_error());
}
echo "Connection successfully";
Here, the username and password are the credentials used by the database server to verify identity.
In order to ensure security, the database server will authenticate each connection request. When the connect() function sends a connection request, the database server compares the incoming username and password:
The user name does not exist : the database cannot find the account corresponding to the user name, so the connection is naturally refused.
Password error : Connection will be refused even if the username exists and password verification fails.
Therefore, as long as there is any spelling error in the user name or password, the database server will reject the connection request, and the PHP side will receive an error message, causing the connection to fail.
When the connection fails, the mysqli_connect_error() function will return specific error messages, for example:
Access denied for user 'wronguser'@'localhost' (using password: YES)
This indicates a username or password error.
Confirm the accuracy of the username and password to avoid spelling errors.
You can store username and password in configuration files to avoid errors caused by hard coding.
Use debug information to view error prompts to quickly locate problems.
Try to avoid escape errors caused by special characters in the password.
