You can use PHP and MySQL together in a single file to perform various database operations. Here’s a step-by-step guide on how to do this using procedural style in PHP:

Steps to Use PHP and MySQL in a Single File

1. Establish a Database Connection
2. Execute SQL Queries
3. Fetch Results
4. Close the Connection

Here’s an example that demonstrates how to connect to a MySQL database, execute a query, and fetch results using procedural PHP:

Example: Fetching Data from a MySQL Database

<?php
// Step 1: Establish a Database Connection
$servername = "localhost"; // Replace with your database server name
$username = "root";        // Replace with your database username
$password = "";            // Replace with your database password
$dbname = "test";          // Replace with your database name

// Create connection
$conn = mysqli_connect($servername, $username, $password, $dbname);

// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

// Step 2: Execute SQL Query
$sql = "SELECT id, name, email FROM users"; // Replace with your SQL query
$result = mysqli_query($conn, $sql);

// Step 3: Fetch Results
if (mysqli_num_rows($result) > 0) {
    // Output data of each row
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Email: " . $row["email"]. "<br>";
    }
} else {
    echo "0 results";
}

// Step 4: Close the Connection
mysqli_close($conn);
?>

Explanation

1. Establish a Database Connection:

   • Use mysqli_connect() to connect to the MySQL database.
   • Check if the connection is successful; if not, display an error message.

2. Execute SQL Query:

   • Write your SQL query as a string and execute it using mysqli_query().
   • mysqli_query() returns a result set for SELECT queries, or TRUE for INSERT, UPDATE, and DELETE queries.

3. Fetch Results:

   • Use mysqli_num_rows() to check if there are any rows in the result set.
   • Loop through the result set with mysqli_fetch_assoc() to fetch rows as associative arrays.
   • Output the data as needed.

4. Close the Connection:

   • Use mysqli_close() to close the connection to the MySQL database.

Additional Operations

You can perform other operations such as inserting, updating, or deleting records using similar procedures. Here's an example of inserting a new record:

<?php
// Establish a Database Connection
$conn = mysqli_connect($servername, $username, $password, $dbname);

// Check connection
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}

// Insert Data
$sql = "INSERT INTO users (name, email) VALUES ('John Doe', 'john@example.com')";
if (mysqli_query($conn, $sql)) {
    echo "New record created successfully";
} else {
    echo "Error: " . $sql . "<br>" . mysqli_error($conn);
}

// Close the Connection
mysqli_close($conn);
?>

Summary

• Establish a connection: Use mysqli_connect() to connect to the database.
• Execute a query: Use mysqli_query() to run your SQL query.
• Fetch results: Use mysqli_fetch_assoc() to retrieve rows.
• Close the connection: Use mysqli_close() to close the database connection.