How to Quickly Get Row Count in PHP MySQLi Queries with mysqli_num_rows

When working with PHP and MySQL, you may need to know how many rows a query returned. PHP provides the convenient mysqli_num_rows function for this purpose.

Below is a complete example demonstrating how to use mysqli_num_rows to obtain the row count from a result set:

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

// Check if the connection was successful
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);

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

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

In the example, we first connect to the database, execute a SELECT query, and store the result in $result. Then we call mysqli_num_rows($result) to retrieve the row count and store it in $num_rows. Finally, we echo the count to the page.

Note that mysqli_num_rows should only be used after a query has executed successfully; if the query fails, the result set contains no data and the function will return 0.

Summary

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