pg_result_error

pg_result_error does NOT work with prepared statements.

So considering pg_query and pg_query_params don't return results on error, and that this would be an extremely handy thing to have, I just ended up writing my own functions wrapping the pg_send_* ones to work like the aforementionned two <em>should</em>. There's not a whole lot of code to them, the comments are mostly references from the libPQ and PHP doc, to explain the behavior.
<?php
class PostgresConnectionError extends Exception {
 public function __construct($last_error) {
 parent::__construct($message);
 }
}
function pg_send_query_sync($connection, string $query) {
 // This function cannot work if any query is already running for that connection because the results may then get mixed up.
 assert(pg_get_result($connection) === false);
 $dispatch_ok = pg_send_query($connection, $query);
 // The *only* case where nothing can be returned, when the connection fails to dispatch the initial query.
 if (!$dispatch_ok) throw new PostgresConnectionError(pg_​last_​error($connection));
 // From the libPQ doc : "PQgetResult must be called repeatedly until it returns a null pointer, indicating that the command is done."
 // In the case of pg_query/PQExec, which we're trying to emulate:
 // "Note however that the returned PGresult structure describes only the result of the last command executed from the string."
 // "Should one of the commands fail, processing of the string stops with it and the returned PGresult describes the error condition."
 while ($result = pg_get_result($connection)) {
 // Drain all results on the connection and only return the last one.
 if ($last_result) pg_free_result($last_result);
 $last_result = $result;
 }
 assert(is_resource($result) && get_resource_type($result) === "pgsql result");
 return $last_result;
}
function pg_send_query_params_sync($connection, string $query, array $params) {
 // This function cannot work if any query is already running for that connection because the results may then get mixed up.
 assert(pg_get_result($connection) === false);
 $dispatch_ok = pg_send_query_params($connection, $query, $params);
 // The *only* case where nothing can be returned, when the connection fails to dispatch the initial query.
 if (!$dispatch_ok) throw new PostgresConnectionError(pg_​last_​error($connection));
 // From the libPQ doc : "PQgetResult must be called repeatedly until it returns a null pointer, indicating that the command is done."
 
 // In the case of pg_query_params/PQExecParams, which we're trying to emulate:
 // "Unlike PQexec, PQexecParams allows at most one SQL command in the given string. (There can be semicolons in it, but not more than one nonempty command.)"
 while ($result = pg_get_result($connection)) {
 // Drain all results on the connection, although there should only be one.
 if ($last_result) pg_free_result($last_result);
 $last_result = $result;
 }
 assert(is_resource($result) && get_resource_type($result) === "pgsql result");
 return $last_result;
}

You can use pg_set_error_verbosity() to retrieve SQLSTATUS from pg_last_error().

Because pg_query() returns FALSE if the query fails, you must must use pg_send_query() and pg_get_result() to get the result handle.
PostgreSQL 7.4 introduced a new function called PQresultErrorField() that can be used to get SQLSTATE code from a query, which is far more useful than the error string returned from pg_result_error().
http://www.postgresql.org/docs/7.4/static/libpq-exec.html
http://www.postgresql.org/docs/7.4/static/errcodes-appendix.html
Here's a patch that adds the pg_result_error_field() function to PHP:
http://collapsed.net/patches/php-4.3.5RC3-pg_result_error_field.diff
(To apply the patch cd into your php-4.3.5RC directory and type: patch -p1 </path/to/php-4.3.5RC3-pg_result_error_field.diff)
Example code:
<?php
 if(!($db = pg_connect("user=foo password=bar dbname=foobar")))
 die("pg_connect");
 if(!pg_send_query($db, "SELECT foo FROM bar"))
 die("pg_send_query");
 if(!($result = pg_get_result($db)))
 die("pg_get_result");
 echo(pg_result_error($result) . "<br />\n");
 /* only available if you have patched php */
 if(function_exists("pg_result_error_field"))
 {
 $fieldcode = array(
 "PGSQL_DIAG_SEVERITY", "PGSQL_DIAG_SQLSTATE",
 "PGSQL_DIAG_MESSAGE_PRIMARY", "PGSQL_DIAG_MESSAGE_DETAIL",
 "PGSQL_DIAG_MESSAGE_HINT", "PGSQL_DIAG_STATEMENT_POSITION",
 "PGSQL_DIAG_CONTEXT", "PGSQL_DIAG_SOURCE_FILE",
 "PGSQL_DIAG_SOURCE_LINE", "PGSQL_DIAG_SOURCE_FUNCTION");
 foreach($fieldcode as $fcode)
 {
 printf("%s: %s<br />\n",
 $fcode,
 pg_result_error_field($result, constant($fcode)));
 }
 pg_free_result($result);
 }
?>

<?php pg_result_error_field($result, PGSQL_DIAG_SQLSTATE); ?>
Returns the SQLSTATE code.