How to Count Rows in a MySQL Result Set with PHP’s mysqli_num_rows

When performing database operations with PHP, you may need to obtain the number of rows in a result set. PHP provides the convenient function mysqli_num_rows for this purpose.

Below is a sample code demonstrating how to use mysqli_num_rows to get the row count of a result set:

<?php
// Assume a connection to the database has been established
$mysqli = new mysqli('localhost', 'username', 'password', 'database_name');

// Check if the connection succeeded
if ($mysqli->connect_errno) {
    echo "Failed to connect to database: " . $mysqli->connect_error;
    exit();
}

// Execute a query
$query = "SELECT * FROM users";
$result = $mysqli->query($query);

// Verify the query succeeded
if (!$result) {
    echo "Query failed: " . $mysqli->error;
    exit();
}

// Use mysqli_num_rows to get the number of rows in the result set
$num_rows = mysqli_num_rows($result);

// Print the result
echo "Number of rows in the result set: " . $num_rows;

// Close the connection
$mysqli->close();
?>

In the example above, we first connect to the database, then execute a query and store the result set in $result. We then call mysqli_num_rows to obtain the row count, storing it in $num_rows, and finally output the count with echo.

Note that mysqli_num_rows can only be used after a successful query; if the query fails, the result set contains no data and the function returns 0.

Summary

Using PHP’s mysqli_num_rows function makes it easy to retrieve the number of rows in a result set, which is useful for determining whether data was returned and for counting query results.