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:

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$ cockroach start --insecure \
--store=hello-1 \
--host=localhost

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.

In a new terminal, start node 2:

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$ cockroach start --insecure \
--store=hello-2 \
--host=localhost \
--port=26258 \
--http-port=8081 \
--join=localhost:26257

In a new terminal, start node 3:

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$ cockroach start --insecure \
--store=hello-3 \
--host=localhost \
--port=26259 \
--http-port=8082 \
--join=localhost:26257

Step 3. Create a user

In a new terminal, as the root user, use the cockroach user command to create a new user, maxroach.

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$ cockroach user set maxroach --insecure

Step 4. Create a database and grant privileges

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

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$ cockroach sql --insecure -e 'CREATE DATABASE bank'

Then grant privileges to the maxroach user.

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$ cockroach sql --insecure -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.

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

Step 6. Run the PHP code

Now that you have a database and a user, you'll run code to create a table and insert some rows, and then you'll run code to read and update values as an atomic transaction.

Basic Statements

First, use the following code to connect as the maxroach user and execute some basic SQL statements, inserting rows and reading and printing the rows.

Download the basic-sample.php file, or create the file yourself and copy the code into it.

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<?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)

Next, use the following code to again connect as the maxroach user but this time execute 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.

Download the txn-sample.php file, or create the file yourself and copy the code into it.

With the default SERIALIZABLE isolation level, CockroachDB may require the client to retry a transaction in case of read/write 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.
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<?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, use the built-in SQL client to verify that funds were transferred from one account to another:

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$ cockroach sql --insecure -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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