How to Replicate mysql_num_rows Functionality Using PDO?

Using PDO to Replace mysql_num_rows

Question:

Reworking a PHP application to use PDO, developers may encounter the need to replicate the functionality of mysql_num_rows for counting the number of rows in a result set. How can this be achieved using PDO?

Answer:

PDO provides two methods to count rows:

Method 1: Direct Query

<code class="php">$res = $DB->query('SELECT COUNT(*) FROM table');
$num_rows = $res->fetchColumn();</code>

Method 2: Prepared Statement

<code class="php">$res = $DB->prepare('SELECT COUNT(*) FROM table');
$res->execute();
$num_rows = $res->fetchColumn();</code>

Data Existence Check

In addition to row counting, these methods can be used to check for data existence:

<code class="php">$res = $DB->query('SELECT COUNT(*) FROM table');
$data_exists = ($res->fetchColumn() > 0) ? true : false;</code>

Example Use Case

To determine if there is only one row in a table, the following code can be used:

<code class="php">$res = $DB->query('SELECT COUNT(*) FROM table');
$message = ($res->fetchColumn() > 0) ? array('status' => 'ok') : array('status' => 'error');</code>

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