PHP MySQLi mysqli_query() - Executing Queries

mysqli_query()

The mysqli_query() function is used to execute queries (SQL commands) in the database. The result of the function depends on the command type: for SELECT it returns a result object, while for INSERT/UPDATE/DELETE it returns TRUE or FALSE.

EXAMPLE

<?php
$server = "localhost";
$username = "root";
$password = "";
$database = "mysqli_database";

$connection = mysqli_connect($server, $username, $password, $database);

if (mysqli_connect_errno()) {
    echo "Connection failed: " . mysqli_connect_error();
    exit();
}

// Execute query to read data
$sql = "SELECT * FROM mysqli_table";

// NOTE: The mysqli_query() function accepts the connection and the SQL string. Since this is a 
// SELECT command, it returns a special result object (if it were an INSERT or UPDATE command, 
// it would only return true/false). We then pass this object to functions for counting or reading rows.
if ($result = mysqli_query($connection, $sql)) {
    // Output the number of rows found
    echo "There are " . mysqli_num_rows($result) . " rows in the table.";
    
    // Always free the result from memory
    mysqli_free_result($result);
}

mysqli_close($connection);
?>

RESULT

The result will be displayed here...

Practical use: This is the most frequently used function for interacting with the database. It allows us to read data, add new records, and modify existing ones. The function also accepts an optional third parameter (e.g., MYSQLI_ASYNC) if asynchronous execution is desired.

It returns a result object for successful SELECT, SHOW, or DESCRIBE queries.

It returns TRUE for other successful queries (e.g., INSERT) and FALSE on error.

It is very important to free the memory using mysqli_free_result() after reading the results.