Aaron As a Chimp

So, with the release of PHP 5.3 some of the new features got me thinking about better ways to query and interact with data. I’m tentatively calling it bbQuery, or bbQ for short.

Data Driven Apps

Web applications are typically driven by data and interactions between it. A typical situation involves: Querying data from the database, formatting as HTML, outputting. A few years ago it was just that simple. Today you have JSON, RSS, and other various formats.

Going by the standard model, you have to create each page separately for all of the various formats, duplicating code. I can’t say I solved this problem entirely, but I’m getting close.

Grab the Steaks, It’s Time for a bbQ

The goal is to be functionally similar to SQL but include a formatting layer that intelligently determines the way to display the data. The following snippet show how the old model can be transitioned to bbQ.

$DB('Children')
   ->select('children_id', 'dob', 'fitness', 'status')
   ->format(function ($row) {
      echo "${row['dob']} - ${row['fitness']} - ${row['status']}";
   });

A simple example using the gFonted database. The first line selects the table from the database. On the second we select the columns we want in the query. The query results are then returned in to a callback from the format function. Very quickly you could create predefined formatting functions.

$DB('Children')
   ->select('*')
   ->left_join('Template', 'children_id')
   ->format(bbQuery::format_table); // predefined format functions

But thats far from automatic, intelligent maybe. Its impossible to guess what format anyone will need. There are a few generic formats (JSON and XML) that could be dealt with automatically.

$DB('Children')
   ->select('*')
   ->left_join('Template', 'children_id')
   ->limit(5)
   ->order_by('fitness', bbQuery::asc) // bbQuery::asc == "asc"
   ->set_type("application/json")
   ->format();
 
$DB('Children')
   ->select('*')
   ->left_join('Template', 'children_id')
   ->limit(5) // is a variable that gets overwritten
   ->order_by('fitness', bbQuery::desc) // order by's are string
   ->order_by('dob', bbQuery::asc) // and gets appended to
   ->set_type("application/xml")
   ->format();

Going the Other Direction

Sometimes its useful to put data into a database. I guess thats an understatement. Its also an understatement to say that doing so is a simple task. An example of standard data insertion:

$DB('Correct')
   ->insert_into('children_id', 'correct')  // returns an insert object
   ->values(12, false);

However this could be greatly simplified. MySQL already knows the datatype for the column, so validation could be automated. The data could even be automatically inserted from a form.

<form>
   <input name="children_id" type="text" value="12" />
   <input name="correct" type="checkbox" />
</form>
 
<?
$DB['Children']
   ->insert_into('children_id',  'correct')  // returns an insert object
   ->from_form();
?>

And finally some other useful snippets:

$DB->query("select * from Children")
    ->format(bbQuery::format_table);
 
$DB('test')
   ->create_table() // returns a create_table object
   ->column('test_id', bbQuery::id_column()) // id is special if set as a primary key, unsigned integer autoincrement
   ->column('test_foreign_id', bbQuery::id_column()) // just a unsigned integer
   ->column('test_char', bbQuery::char_column(10)) // field length as parameter
   ->column('test_int', bbQuery::integer_column(bbQuery::big), 0) // default as third parameter to column
   ->column('test_enum', bbQuery::enum_column('val', 'val3', 'val2')) // enum is varidaic
   ->primary_key('test_id')
   ->foreign_key('test_foreign_id', 'Correct');
 
$DB('test')
   ->alter_table() // returns a alter_table object
   ->add('test_timestamp', bbQuery::timestamp_column, bbQuery::now)
   ->drop('test_int');
 
$DB->query("truncate table test"); // format is not appropriate here

In my last post I wrote about JavaScript variables.  It stemmed from realizing that the dollar sign ($) was a valid character in JavaScript.  I struggled to find any use for all of these new characters – other than making code unreadable.  One thing stuck out in my mind.  An old episode of Hak .5 where Billy Hoffman described a worm that would be written in a hybrid of Perl and JavaScript.  A Dr. Jekyll and Mr. Hyde scenario where the worm would embed itself in a web page and search for a “host”, and then infect that host.  That host would then serve pages with the worm embedded in it, creating exponential growth.  Unfortunately at the time he didn’t have a proof of concept.

Hybrid Means Better Gas Mileage

Unlike Billy’s technique I chose to use PHP instead of Perl.  Many of the language constructs are identical between PHP and JavaScript.  However there are few snags.

• PHP scripts have to start and end with ‘<?’ and ‘?>’ respectively.
• PHP variables must start with a ‘$’.
• Most of JavaScript’s standard functions are wrapped in objects.  Math, String, etc.
• PHP uses the ‘.’ for concatenation, while JavaScript uses ‘+’.
• PHP uses C++ style definition for objects, while JavaScript uses a prototype definition.
• JavaScript uses the C++ style const keyword to define constants, while PHP uses the define() function.

The Lucky Ones

Not all of these problems can be worked around, but enough of them can be worked around that functioning code can be written.

PHP scripts have to start and end with ‘<?’ and ‘?>’ respectively.

The workaround for this is to run the script using the eval() function.  The PHP’s eval() function doesn’t require the opening and closing tags as feature.

PHP variables must start with a ‘$’.

The dollar sign is a valid character in JavaScript variables, so starting them with the dollar sign poses no problem.

Most of JavaScript’s standard functions are wrapped in objects.  Math, String, etc.

PHP.js can be used to wrap the standard JavaScript functions.  Acting as a compatibility layer.

JavaScript uses the C++ style const keyword to define constants, while PHP uses the define() function.

PHP version 5.3.0 allows for the const keyword.

Taking the Plunge

As a proof of concept I wrote a small function to calculate  the great circle distance.  It computes the distance in both PHP and JavaScript.  You can find it here and hybrid PHP / JavaScript code here.