This tutorial shows you how build a simple PHP application with CockroachDB using a PostgreSQL-compatible driver. We’ve tested and can recommend the php-pgsql driver, so that driver is featured here.

Before You Begin

Make sure you have already installed CockroachDB.

Step 1. Install the php-pgsql driver

Install the php-pgsql driver as described in the official documentation.

Step 2. Start a cluster

For the purpose of this tutorial, you need only one CockroachDB node running in insecure mode:

# Start node 1:
$ cockroach start --background \
--store=hello-1

But as you might’ve seen in the Start a Local Cluster tutorial, it’s incredibly easy to start and join addition nodes, if you want to simulate a real cluster:

# Start node 2:
$ cockroach start --background \
--store=hello-2 \
--port=26258 \
--http-port=8081 \
--join=localhost:26257

# Start node 3:
$ cockroach start --background \
--store=hello-3 \
--port=26259 \
--http-port=8082 \
--join=localhost:26257

Step 3. Create a user

As the root user, use the cockroach user command to create a new user, maxroach.

$ cockroach user set maxroach

Step 4. Create a database and grant privileges

As the root user, use the built-in SQL client to create a bank database.

$ cockroach sql -e 'CREATE DATABASE bank'

Then grant privileges to the maxroach user

$ cockroach sql -e 'GRANT ALL ON DATABASE bank TO maxroach'

Step 5. Create a table in the new database

As the maxroach user, use the built-in SQL client to create an accounts table in the new database.

$ cockroach sql --database=bank --user=maxroach -e \
'CREATE TABLE accounts (id INT PRIMARY KEY, balance INT)'
CREATE TABLE

Step 6. Run the PHP code

Basic Statements

The following code connects as the maxroach user and executes some basic SQL statements, inserting rows and reading and printing the rows.

Copy the code or download it directly.

<?php
try {
  $dbh = new PDO('pgsql:host=localhost;port=26257;dbname=bank;sslmode=disable',
    'maxroach', null, array(
      PDO::ATTR_ERRMODE          => PDO::ERRMODE_EXCEPTION,
      PDO::ATTR_EMULATE_PREPARES => true,
  ));

  $dbh->exec('INSERT INTO accounts (id, balance) VALUES (1, 1000), (2, 250)');

  print "Account balances:\r\n";
  foreach ($dbh->query('SELECT id, balance FROM accounts') as $row) {
      print $row['id'] . ': ' . $row['balance'] . "\r\n";
  }
} catch (Exception $e) {
    print $e->getMessage() . "\r\n";
    exit(1);
}
?>

Transaction (with retry logic)

The following code again connects as the maxroach user but this time executes a batch of statements as an atomic transaction to transfer funds from one account to another, where all included statements are either committed or aborted.

Copy the code or download it directly.

Because the CockroachDB transaction model requires the client to initiate retries in the case of contention, CockroachDB provides a generic retry function that runs inside a transaction and retries it as needed. You can copy and paste the retry function from here into your code. For more details, see Transaction Retries.
<?php

function transferMoney($dbh, $from, $to, $amount) {
  try {
    $dbh->beginTransaction();
    // This savepoint allows us to retry our transaction.
    $dbh->exec("SAVEPOINT cockroach_restart");
  } catch (Exception $e) {
    throw $e;
  }

  while (true) {
    try {
      $stmt = $dbh->prepare(
        'UPDATE accounts SET balance = balance + :deposit ' .
        'WHERE id = :account AND (:deposit > 0 OR balance + :deposit >= 0)');

      // First, withdraw the money from the old account (if possible).
      $stmt->bindValue(':account', $from, PDO::PARAM_INT);
      $stmt->bindValue(':deposit', -$amount, PDO::PARAM_INT);
      $stmt->execute();
      if ($stmt->rowCount() == 0) {
        print "source account does not exist or is underfunded\r\n";
        return;
      }

      // Next, deposit into the new account (if it exists).
      $stmt->bindValue(':account', $to, PDO::PARAM_INT);
      $stmt->bindValue(':deposit', $amount, PDO::PARAM_INT);
      $stmt->execute();
      if ($stmt->rowCount() == 0) {
        print "destination account does not exist\r\n";
        return;
      }

      // Attempt to release the savepoint (which is really the commit).
      $dbh->exec('RELEASE SAVEPOINT cockroach_restart');
      $dbh->commit();
      return;
    } catch (PDOException $e) {
      if ($e->getCode() != '40001') {
        // Non-recoverable error. Rollback and bubble error up the chain.
        $dbh->rollBack();
        throw $e;
      } else {
        // Cockroach transaction retry code. Rollback to the savepoint and
        // restart.
        $dbh->exec('ROLLBACK TO SAVEPOINT cockroach_restart');
      }
    }
  }
}

try {
  $dbh = new PDO('pgsql:host=localhost;port=26257;dbname=bank;sslmode=disable',
    'maxroach', null, array(
      PDO::ATTR_ERRMODE          => PDO::ERRMODE_EXCEPTION,
      PDO::ATTR_EMULATE_PREPARES => true,
    ));

  transferMoney($dbh, 1, 2, 10);

  print "Account balances after transfer:\r\n";
  foreach ($dbh->query('SELECT id, balance FROM accounts') as $row) {
      print $row['id'] . ': ' . $row['balance'] . "\r\n";
  }
} catch (Exception $e) {
    print $e->getMessage() . "\r\n";
    exit(1);
}
?>

After running the code, to verify that funds were, in fact, transferred from one account to another, you can again use the built-in SQL client:

$ cockroach sql -e 'SELECT id, balance FROM accounts' --database=bank
+----+---------+
| id | balance |
+----+---------+
|  1 |     900 |
|  2 |     350 |
+----+---------+
(2 rows)

What’s Next?

Read more about using the php-pgsql driver.

You might also be interested in using a local cluster to explore the following core CockroachDB features:



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