In this source code example, we will see how to retrieve records (using SELECT Query with an ORDER BY Clause) from a database table in PHP using MySQLi.

PHP MySQL ORDER BY Clause

<?php
/* Attempt MySQL server connection. Assuming you are running MySQL
server with default setting (user 'root' with no password) */
$host= "localhost";
$username= "root";
$password = "";

$db_name = "demo_db";

$mysql_connection = mysqli_connect($host, $username, $password, $db_name);
 
// Check connection
if ($mysql_connection->connect_errno) {
    printf("connection failed: %s\n", $mysql_connection->connect_error());
    exit();
}
 
// Attempt select query execution with order by clause
$sql = "SELECT * FROM students ORDER BY email";
if($result = mysqli_query($mysql_connection, $sql)){
    if(mysqli_num_rows($result) > 0){
        echo "<table>";
            echo "<tr>";
                echo "<th>id</th>";
                echo "<th>first_name</th>";
                echo "<th>last_name</th>";
                echo "<th>email</th>";
            echo "</tr>";
        while($row = mysqli_fetch_array($result)){
            echo "<tr>";
                echo "<td>" . $row['id'] . "</td>";
                echo "<td>" . $row['first_name'] . "</td>";
                echo "<td>" . $row['last_name'] . "</td>";
                echo "<td>" . $row['email'] . "</td>";
            echo "</tr>";
        }
        echo "</table>";
        // Close result set
        mysqli_free_result($result);
    } else{
        echo "No records matching your query were found.";
    }
} else{
    echo "ERROR: Could not able to execute $sql. " . mysqli_error($mysql_connection);
}
 
// Close connection
mysqli_close($mysql_connection);
?>

Let's understand the above PHP script.

The mysqli_connect() function opens a new connection to the MySQL server:

$host= "localhost";
$username= "root";
$password = "";

$db_name = "demo_db";

$mysql_connection = mysqli_connect($host, $username, $password, $db_name);

SQL SELECT query with an ORDER BY clause to retrieve records from the database table:

// Attempt select query execution with order by clause
$sql = "SELECT * FROM students ORDER BY email";

The mysqli_query() function performs a query against a database:

if($result = mysqli_query($mysql_connection, $sql)){}

The mysqli_num_rows() function returns the number of rows in a result set:

if(mysqli_num_rows($result) > 0){
        echo "<table>";
            echo "<tr>";
                echo "<th>id</th>";
                echo "<th>first_name</th>";
                echo "<th>last_name</th>";
                echo "<th>email</th>";
            echo "</tr>";
        while($row = mysqli_fetch_array($result)){
            echo "<tr>";
                echo "<td>" . $row['id'] . "</td>";
                echo "<td>" . $row['first_name'] . "</td>";
                echo "<td>" . $row['last_name'] . "</td>";
                echo "<td>" . $row['email'] . "</td>";
            echo "</tr>";
        }
        echo "</table>";
        // Close result set
        mysqli_free_result($result);
    } else{
        echo "No records matching your query were found.";
    }

Closing MySQL server connection:

// Close connection
mysqli_close($mysql_connection);