Author: admin

One common situation in web developing is that you want to expand and collapse an element (maybe a DIV) with a smooth animation. It’s a common request because having a smooth animation helps the user to follow what happens on the page without being disorientated by fast changes. Read more

Google APIs are great. You can do almost everything with them: data reporting, file upload, everything. Unfortunately the documentation isn’t that good because same very important informations are not reported there! So you try the examples and they don’t work because of a hidden step you didn’t done. Read more

PDO is a great OO library for interacting with your database from PHP. It has a very consistent interface and your code will be cleaner than ever. And your PHP script will be more portable because PDO is not related to any database, but is a generic library to work with MySQL, PostgreSQL, SQLite and a lot others.

The only thing I miss in PDO is a better query error management. When I execute a query I have to check every time the PDOStatement->errorCode property to get sure everything is working well. That’s very annoying.

Fortunately there is a way to extend the PDOStatement class to get more comfortable in writing our script. In the official docs there is not a lot about this, but here is an explanation.

The official documentation talks only about a PDO::ATTR_STATEMENT_CLASS attribute for the PDO instance to be set through the setAttribute method. That’s not much, but here is an example:

try {
  $dbh = new PDO(
    "mysql:dbname=my_database;host=localhost;charset=utf8",
    $user,
    $pass
  );
  $dbh->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('MyPDOStatement'));
} catch (PDOException $e) {
  die('Connection failed: ' . $e->getMessage());
}

You can set the attribute after the connection, not a problem. MyPDOStatement is a custom class that extends PDOStatement. A minimal version will look like this:

class MyPDOStatement extends PDOStatement
{
  private function __construct() {}

  function execute($input = array()) {
    parent::execute($input);

    if ($this->errorCode() !== '00000') {
      $err = $this->errorInfo();
      error_log(SQLException($err[2], $err[1]));
      return false;
    }

    return true;
  }
}

The private constructor is mandatory. You can use it to pass some variable to every MyPDOStatement instance, very useful in many situations.

For example we could use an array to track query execution times. So the code will look like this:

$info = array('queries' => 0, 'query_time' => 0);

try {
  $dbh = new PDO(
    "mysql:dbname=my_database;host=localhost;charset=utf8",
    $user,
    $pass
  );
  $dbh->setAttribute(PDO::ATTR_STATEMENT_CLASS, array('MyPDOStatement', array($info)));
} catch (PDOException $e) {
  die('Connection failed: ' . $e->getMessage());
}

class MyPDOStatement extends PDOStatement
{
  private $info;

  private function __construct(&info) {
    $this->info = &$info;
  }

  function execute($input = array()) {
    $t = microtime(true);
    parent::execute($input);
    $t = microtime(true) - $t;

    if ($this->errorCode() !== '00000') {
      $err = $this->errorInfo();
      error_log(SQLException($err[2], $err[1]));
      return false;
    }

    $this->info['queries']++;
    $this->info['query_time'] += $t;

    return true;
  }
}

Perl is an awesome language. I like it very much more than Python because you can put some imagination inside your code, doing things with your style. I like very much the loose typing because you don’t have to care about the content in your variables: numbers, strings, objects are almost the same. You have to care about what you are doing, not how.

Commenting your code is very important for you and for everybody else that will see it. And if you are writing a standalone script it’s very useful to give hints about the usage without reading the code. Perl has a integrated comment system called Pod that can be used to generated documentation files in a number of format, but how can you display something on the command line by using the common –help parameter?

The answer is the Pod::Usage package. It’s a very powerful package, but I will use it in a minimal way. The official documentation will tell you everything you need to know, but let’s take a taste.

#!/usr/bin/perl
=head1 Example script

This is an example script to taste the Pod::Usage package.

=head1 SYNOPSIS

example.pl [--help] --source=1.2.3.4 --target=5.6.7.8

Options:
--help Displays this help
--source A source
--target A target

=cut

use strict;
use Getopt::Long;
use Pod::Usage;

my ($help, $source, $target);

GetOptions(
'source=s' => $source,
'target=s' => $target,
'help' => $help
);

pod2usage(1) if $help;

[...]

So how does this work? I use the Getopt::Long package to manage command line parameters. I pass two string parameters (source, target) and a flag (help). If flag is set I call the pod2usage function from Pod::Usage with a ‘1’ as parameter. The function will print out everything contained inside the SYNOPSYS paragraph and will exit the script with code 1 (or whatever number you passed).  That’s all!