This tutorial shows you how build a simple PHP application with CockroachDB using a PostgreSQL-compatible driver.
We have tested the php-pgsql driver enough to claim beta-level support, so that driver is featured here. If you encounter problems, please open an issue with details to help us make progress toward full support.
Before you begin
- Install CockroachDB.
- Start up a secure or insecure local cluster.
- Choose the instructions that correspond to whether your cluster is secure or insecure:
Step 1. Install the php-pgsql driver
Install the php-pgsql driver as described in the official documentation.
Step 2. Create the maxroach user and bank database
Start the built-in SQL client:
$ cockroach sql --certs-dir=certs
In the SQL shell, issue the following statements to create the maxroach user and bank database:
> CREATE USER IF NOT EXISTS maxroach;
> CREATE DATABASE bank;
Give the maxroach user the necessary permissions:
> GRANT ALL ON DATABASE bank TO maxroach;
Exit the SQL shell:
> \q
Step 3. Generate a certificate for the maxroach user
Create a certificate and key for the maxroach user by running the following command. The code samples will run as this user.
$ cockroach cert create-client maxroach --certs-dir=certs --ca-key=my-safe-directory/ca.key
Step 4. 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.
<?php
try {
$dbh = new PDO('pgsql:host=localhost;port=26257;dbname=bank;sslmode=require;sslrootcert=certs/ca.crt;sslkey=certs/client.maxroach.key;sslcert=certs/client.maxroach.crt',
'maxroach', null, array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_EMULATE_PREPARES => true,
PDO::ATTR_PERSISTENT => 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 $e->getMessage() . "\r\n";
exit(1);
}
?>
The output should be:
Account balances:
1: 1000
2: 250
Transaction (with retry logic)
Next, use the following code to again connect as the maxroach user but this time execute a batch of statements as an atomic transaction to transfer funds from one account to another, where all included statements are either committed or aborted.
Download the txn-sample.php file, or create the file yourself and copy the code into it.
CockroachDB may require the client to retry a transaction in case of read/write contention. CockroachDB provides a generic retry function that runs inside a transaction and retries it as needed. You can copy and paste the retry function from here into your code.
<?php
function transferMoney($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 {
$dbh = new PDO('pgsql:host=localhost;port=26257;dbname=bank;sslmode=require;sslrootcert=certs/ca.crt;sslkey=certs/client.maxroach.key;sslcert=certs/client.maxroach.crt',
'maxroach', null, array(
PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
PDO::ATTR_EMULATE_PREPARES => true,
));
transferMoney($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);
}
?>
The output should be:
Account balances after transfer:
1: 900
2: 350
To verify that funds were transferred from one account to another, use the built-in SQL client:
$ cockroach sql --certs-dir=certs -e 'SELECT id, balance FROM accounts' --database=bank
+----+---------+
| id | balance |
+----+---------+
| 1 | 900 |
| 2 | 350 |
+----+---------+
(2 rows)
Step 2. Create the maxroach user and bank database
Start the built-in SQL client:
$ cockroach sql --insecure
In the SQL shell, issue the following statements to create the maxroach user and bank database:
> CREATE USER IF NOT EXISTS maxroach;
> CREATE DATABASE bank;
Give the maxroach user the necessary permissions:
> GRANT ALL ON DATABASE bank TO maxroach;
Exit the SQL shell:
> \q
Step 3. 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.
<?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,
PDO::ATTR_PERSISTENT => 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 $e->getMessage() . "\r\n";
exit(1);
}
?>
The output should be:
Account balances:
1: 1000
2: 250
Transaction (with retry logic)
Next, use the following code to again connect as the maxroach user but this time execute a batch of statements as an atomic transaction to transfer funds from one account to another, where all included statements are either committed or aborted.
Download the txn-sample.php file, or create the file yourself and copy the code into it.
CockroachDB may require the client to retry a transaction in case of read/write contention. CockroachDB provides a generic retry function that runs inside a transaction and retries it as needed. You can copy and paste the retry function from here into your code.
<?php
function transferMoney($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);
}
?>
The output should be:
Account balances after transfer:
1: 900
2: 350
To verify that funds were transferred from one account to another, use the built-in SQL client:
$ 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 the following pages:
- Client Connection Parameters
- Data Replication
- Fault Tolerance & Recovery
- Automatic Rebalancing
- Cross-Cloud Migration
- Follow-the-Workload
- Automated Operations
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