ZEND PHP 5 Certification STUDY GUIDE

Database Programming ” 161
The following illustrates the use of question mark placeholders instead of named
placeholders.
$sql = ’SELECT author.*, book.* FROM author
LEFT JOIN book ON author.id = book.author_id
WHERE author.last_name = ?’;
$stmt = $dbh->prepare($sql);
$stmt->bindParam(1, $author1, PDO::PARAM_STR, 20);
Prepared statements with bound parameters are perhaps among the most useful and
powerful features of PDO.
Transactions With PDO
For databases that natively support transactions, PDO implements transaction functionality
with the PDO::beginTransaction(), PDO::commit(), and PDO::rollBack()
methods. PDO does not try to emulate transactions for those database engines that
do not support them. See the Transactions section earlier in this chapter for more
information on how transactions work.
The following code again shows the full example including the try/catch statements.
If any of the statements executed against the database fail, then PDO
will throw an exeception. When catch catches the the exeception, you can call
PDO::rollBack() to ensure that any actions taken during the transaction are rolled
back. Here, one of the INSERT statements fails to list all columns for which it has values.
Thus, it throws an exeception and the valid INSERT statement executed earlier is
not committed to the database.
try
{
$dsn = ’mysql:host=localhost;dbname=library’;
$dbh = new PDO($dsn, ’dbuser’, ’dbpass’);
$dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, TRUE);
$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
Licensed to 482634 - Amber Barrow (itsadmin@deakin.edu.au)
$dbh->beginTransaction();
$dbh->exec("INSERT INTO book (isbn, title, author_id, publisher_id)
VALUES (’0395974682’, ’The Lord of the Rings’, 1, 3)");
$dbh->exec("INSERT INTO book (title) VALUES (’Animal Farm’, 3, 2)");