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    pg_last_error

    (PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)

    pg_last_error — Get the last error message string of a connection

    Descrição

    pg_last_error(?PgSql\Connection $connection = null): string

    pg_last_error() returns the last error message for a given connection.

    Error messages may be overwritten by internal PostgreSQL (libpq) function calls. It may not return an appropriate error message if multiple errors occur inside a PostgreSQL module function.

    Use pg_result_error(), pg_result_error_field(), pg_result_status() and pg_connection_status() for better error handling.

    Nota:

    This function used to be called pg_errormessage().

    Parâmetros

    connection

    Uma instância de PgSql\Connection. Quando o parâmetro connection for null, a conexão padrão será usada. A conexão padrão é a última conexão feita por pg_connect() ou pg_pconnect().

    Aviso

    A partir do PHP 8.1.0, usar a conexão padrão tornou-se defasado.

    Valor Retornado

    A string containing the last error message on the given connection.

    Registro de Alterações

    Versão Descrição
    8.1.0 O parâmetro connection agora espera uma instância de PgSql\Connection; anteriormente, um resource era esperado.
    8.0.0 connection is now nullable.

    Exemplos

    Exemplo #1 pg_last_error() example

    <?php
    $dbconn     = pg_connect("dbname=publisher") or die("Could not connect");

    // Query that fails
    $res = pg_query($dbconn, "select * from doesnotexist");

    echo     pg_last_error($dbconn);
    ?>

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    User Contributed Notes 1 note

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    5
    Tamas Bolner
    14 years ago
    From a practical view there are two types of error messages when using transactions:

    -"Normal" errors: in this case, the application should stop the current process and show an error message to the user.

    -Deadlock errors. This shows that the deadlock detection process of PostgreSQL found a circle of dependency, and broke it by rolling back the transaction in one of the processes, which gets this error msg. In this case, the application should not stop, but repeat the transaction.

    I found no discrete way to find out which case are we dealing with. This interface doesn't support error codes, so we have to search for patterns in the message text.

    Here is an example for PostgreSQL database connection class. It throws a PostgresException on "normal" errors, and DependencyException in the case of a broken deadlock, when we have to repeat the transaction.

    postgres.php:
    <?php
    class PostgresException extends Exception {
        function     __construct($msg) { parent::__construct($msg); }
    }

    class     DependencyException extends PostgresException {
        function     __construct() { parent::__construct("deadlock"); }
    }

    class     pg {
        public static     $connection;
       
        private static function     connect() {
                self::$connection = @pg_connect("dbname=foodb user=foouser password=foopasswd");
            if (    self::$connection === FALSE) {
                throw(new     PostgresException("Can't connect to database server."));
            }
        }
       
        public static function     query($sql) {
            if (!isset(    self::$connection)) {
                    self::connect();
            }
           
                $result = @pg_query(self::$connection, $sql);
            if (    $result === FALSE) {
                    $error = pg_last_error(self::$connection);
                if (    stripos($error, "deadlock detected") !== false) throw(new DependencyException());
               
                throw(new     PostgresException($error.": ".$sql));
            }
           
                $out = array();
            while ( (    $d = pg_fetch_assoc($result)) !== FALSE) {
                    $out[] = $d;
            }
           
            return     $out;
        }
    }
    ?>

    It should be used in this way:

    test.php:
    <?php
    include("postgres.php");

    do {
            $repeat = false;
        try {
                pg::query("begin");
           
            ...

                $result = pg::query("SELECT * FROM public.kitten");

            ...

                pg::query("commit");
        }
        catch (    DependencyException $e) {
                pg::query("rollback");
                $repeat = true;
        }
    } while (    $repeat);
    ?>

    The normal errors should be caught at the frontend.

    Tamas
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