What is the difference between COUNT, mysqli_num_rows, and PDO synonym in PHP when counting entries in a MySQL table?

When counting entries in a MySQL table in PHP, COUNT is a SQL function that can be used in a query to directly count the number of rows that match certain criteria. mysqli_num_rows is a function specific to the MySQL Improved Extension (mysqli) that counts the number of rows in a result set returned by a SELECT query. PDO does not have a direct synonym for counting rows, but you can use rowCount() method to get the number of rows affected by a query.

// Using COUNT in SQL query
$query = "SELECT COUNT(*) FROM table_name WHERE condition";
$result = mysqli_query($connection, $query);
$row = mysqli_fetch_row($result);
$count = $row[0];

// Using mysqli_num_rows
$query = "SELECT * FROM table_name WHERE condition";
$result = mysqli_query($connection, $query);
$count = mysqli_num_rows($result);

// Using PDO
$query = $pdo->prepare("SELECT * FROM table_name WHERE condition");
$query->execute();
$count = $query->rowCount();