How to Connect Database with PHP

Learn how to establish a connection between PHP and a MySQL database using the mysqli extension

Understand the Problem

Problem Statement

This tutorial demonstrates how to connect a PHP script to a MySQL database. You'll learn to configure database credentials, establish a connection using the mysqli extension, handle connection errors, and properly close the connection. This is a fundamental skill for any PHP developer working with database-driven applications.

Constraints

MySQL server must be running and accessible
Database credentials (host, username, password, database name) must be valid
PHP must have MySQL extension enabled
Connection should be established before performing database operations
Connection should be closed when no longer needed

Examples

Example 1

Input

$host = 'localhost';
$username = 'root';
$password = 'mypassword';
$database = 'test_db';

Output

Connected to the database successfully

Explanation

With valid MySQL credentials and a running MySQL server, the mysqli constructor successfully establishes a connection and outputs the success message.

Example 2

Input

$host = 'localhost';
$username = 'invalid_user';
$password = 'wrong_password';
$database = 'nonexistent_db';

Output

Connection failed: Access denied for user 'invalid_user'@'localhost' (using password: YES)

Explanation

When using invalid credentials or attempting to access a non-existent database, the connection attempt fails and an appropriate error message is displayed.

Solution

/*
 * Note: This is a conceptual C equivalent using MySQL C API
 * PHP's database connectivity is typically not replicated in pure C
 * for web development purposes, but here's how you might approach it
 */

#include <mysql.h>
#include <stdio.h>
#include <stdlib.h>

int main() {
    MYSQL *conn;
    
    // Initialize MySQL connection
    conn = mysql_init(NULL);
    
    if (conn == NULL) {
        fprintf(stderr, "MySQL initialization failed\n");
        return 1;
    }
    
    // Database configuration
    const char *host = "localhost";
    const char *user = "your_username";
    const char *password = "your_password";
    const char *database = "your_database";
    
    // Establish connection
    if (mysql_real_connect(conn, host, user, password, database, 0, NULL, 0) == NULL) {
        fprintf(stderr, "Connection failed: %s\n", mysql_error(conn));
        mysql_close(conn);
        return 1;
    }
    
    printf("Connected to the database successfully\n");
    
    // Perform database operations here
    
    // Close connection
    mysql_close(conn);
    
    return 0;
}

Time:O(1)

Space:O(1)

Approach:

This C code demonstrates the MySQL C API equivalent of the PHP database connection. It initializes a MySQL connection object, configures the database parameters, attempts to connect using mysql_real_connect(), handles connection errors with appropriate error messages, and closes the connection when finished. The mysql.h header provides the necessary MySQL client library functions.

Visual Explanation

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All Problems