How to Use mysqli_num_rows in PHP to Get the Number of Rows in a Result Set

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

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

<?php
// Assume a connection to the database has already 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 that the query executed successfully
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();
?>

The example first establishes a connection to the database, then runs a SELECT query and stores the result in $result . It then calls mysqli_num_rows($result) to obtain the row count, stores it in $num_rows , and echoes the value.

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 determine the number of rows in a result set, which is useful for checking whether data was returned and for counting query results.

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