SQL is often a complicated piece of code by itself, so you may wish put it inside a "here doc."  This will help you read it wherever it appears and test it by itself via a command-line or gui client.

$sql = <<<SQL
SELECT a.foo, b.bar, c.baz
FROM
    table_a a
LEFT JOIN
    table_b b
ON (
    a.a_id = b.a_id
)
JOIN
    table_c c
ON (
    b.c_id = c.c_id
)
WHERE c.name = $1
SQL;

If you decide to deallocate (unprepare) a previously prepared sql command it might be better to quote the sql name as in

  DEALLOCATE "theNameOfMySQL"

instead of (the more natural)

  DEALLOCATE theNameOfMySQL

PostgerSQL preserves the case of your identifiers if, and only if, you quote them. The pg_prepare function preserves the case of the sql name you use.

A complete example would be

  $sql = 'SELECT * FROM user WHERE cod_user = $1';
  $sqlName = 'selectUserByCode';
  if (!pg_prepare ($sqlName, $sql)) {
    die("Can't prepare '$sql': " . pg_last_error());
  }
  $rs = pg_execute($sqlName, array(1));
  do whatever you want with $rs and finally
  $sql = sprintf(
    'DEALLOCATE "%s"',
    pg_escape_string($sqlName)
  );
  if(!pg_query($sql)) {
    die("Can't query '$sql': " . pg_last_error());
  }

I had some problems with this function. When you use pg_prepare() with a function like date_trunc('day', $1) you need to specify the data type.

The solution was use the Pear MDB2 but with some changes in code. The original code try to use pg_prepare() too, with errors.

The given name cannot be the statement itself.
It has a maximum length and will truncate.

If two queries begin the same way, only the first one will be used.

Note that if you are preparing a query with an in clause with a list of items, you will need to prepare each item separately.

$result = pg_prepare($dbconn, "my_query", 'SELECT * FROM shops WHERE name IN($1,$2,$3)');

$result = pg_execute($dbconn, "my_query", array("coffee", "beer", "hard"));

This means that you can't just prepare a query with an arbitrary in() list.

Any error in the prepare is available from pg_last_error().