Candidate Exercise - PHP Developer, for Exads
Solved by Francisco Carvalho
The current solution was implemented using DDD approach.
Domain-driven design (DDD) is the concept that the structure and language of software code (class names, class methods, class variables) should match the business domain.
However, every logic behind required solution for this Exercise is under Domain folder (for all exercises except 3. Database Connectivity - this is preserved under Persistency directory).
DB connection requires the Database configuration under
.envfile. We have a copy of that file under the root directory (named.env.example) - just copy it and fill with right database configuration.
This solution uses composer as a package manager.
To run it locally, you'll need at least PHP 7.4 (the code has some typed properties) and composer installed.
After check it, you can run:
➥ cd /ROOT_DIR_OF_PROJECT
➥ composer installI also used symfony/console package to build Console Application.
Console commands are under Exadsrcise\Application\Commands namespace and only handles the structure of the console command (string description/help, arguments/options) and the logic execution.
In order to execute the program, the user should:
➥ cd /ROOT_DIR_OF_PROJECT
➥ php exadsEvery command could be executed under php exads run:command.
➥ cd /ROOT_DIR_OF_PROJECT
➥ php exads run:fizz-buzz 1 500
Fizz
Fizz
Buzz
Fizz
Fizz
...User could check all the commands doing
➥ cd /ROOT_DIR_OF_PROJECT
➥ php exads listEvery command has an --help option. This gives the information about command usage.
➥ cd /ROOT_DIR_OF_PROJECT
➥ php exads run:fizz-buzz --help
Description:
Write a PHP script that prints all integer values from min to max.
Usage:
run:fizz-buzz <min> <max>
Arguments:
min Min Number
max Max Number
Options:
-h, --help Display this help message
-q, --quiet Do not output any message
-V, --version Display this application version
--ansi Force ANSI output
--no-ansi Disable ANSI output
-n, --no-interaction Do not ask any interactive question
-v|vv|vvv, --verbose Increase the verbosity of messages: 1 for normal output, 2 for more verbose output and 3 for debug
Help:
Write "Fizz" in multiple of three and "Buzz" for the multiples of five.Values which are multiples of both three and five should output as "FizzBuzz".Write a PHP script that prints all integer values from 1 to 100.
For multiples of three output "Fizz" instead of the value and for the multiples of five output "Buzz". Values which are multiples of both three and five should output as "FizzBuzz".
I created the solution under Exadsrcise\Domain\FizzBuzz\NumberRangeChecker class.
use Exadsrcise\Domain\FizzBuzz\NumberRangeChecker;
$numberRangeChecker = new NumberRangeChecker(1, 500);
// Iterate over \Generator
foreach ($numberRangeChecker->fetch() as $number)
echo $number->output();NumberRangeChecker has a method fetch that returns a Generator - this way, we improve the memory used by the application, since we do not need to create the array (keeping it in memory) only to write the desired output.
Write a PHP script to generate a random array of 500 integers (values of 1 – 500 inclusive). Randomly remove and discard an arbitary element from this newly generated array.
Write the code to efficiently determine the value of the missing element. Explain your reasoning with comments.
Assuming we have an unordered array with random repeated numbers, we can solve this using one of two ways:
- Append removed item to a local array - fastest way, do not need to iterate the array;
- Generate an ordered array and check natively with `array_diff function.
I crated the solution under Exadsrcise\Domain\ElementArray\IntegerGenerator class.
findMissingNumbersNatively method is not being used - just be kept for showing solution no. 2.
Demonstrate with PHP how you would connect to a MySQL (InnoDB) database and query for all records with the following fields: (name, age, job_title) from a table called 'exads_test'. Also provide an example of how you would write a sanitised record to the same table.
The solution of this exercise is under Infrastructure/DB class - this is a simple class to abstract both connection and Query (SELECT and INSERT).
It's been used internally in Exadsrcise\Persistency\Repositories\TestRepository class (Repository pattern).
DB class is using .env configuration file to get database connection configuration. Please configure it before use this command, otherwise it will fail.
Take into consideration:
use Exadsrcise\Infrastructure\DB;
// Iterate internally
DB::instance()->selectFrom("exads_test")->all(function($row){
echo $row['name'];
});
// Save rows in memory
$rows = DB::instance()->selectFrom("exads_test")->all();use Exadsrcise\Infrastructure\DB;
// Insert single row
DB::instance()->insertRow('exads_test', ['name', 'age', 'job_title'], ['Francisco', 28, 'Software Developer']);
// Insert multiple rows in a single statement
$rows = [
['Francisco', 28, 'Software Developer'],
['Elon Musk', 49, 'Entrepreneur']
];
DB::instance()->insertRow('exads_test', ['name', 'age', 'job_title'], $rows);The Irish National Lottery draw takes place twice weekly on a Wednesday and a Saturday at 8pm.
Write a function or class that calculates and returns the next valid draw date based on the current date and time AND also on an optionally supplied date and time.
I've created a class Exadsrcise\Domain\Datetime\DatetimeConverter that abstracts the calculation of next date based on given week day.
use Exadsrcise\Domain\Datetime\DatetimeConverter;
$converter = new DatetimeConverter();
$tuesday = $converter->getNextDateOfWeekDay('friday');
echo "The weekend is not so far, is on the next day '{$tuesday->format('Y-m-d')}'";It enables:
- different timezones (given on constructor)
- optionally supplied date and time.
Exads would like to A/B test a number of promotional designs to see which provides the best conversion rate. Write a snippet of PHP code that redirects end users to the different designs based on the database table below. Extend the database model as needed.
i.e. - 50% of people will be shown Design A, 25% shown Design B and 25% shown Design C. The code needs to be scalable as a single promotion may have upwards of 3 designs to test.
| design_id | design_name | split_percent |
|---|---|---|
| 1 | Design 1 | 50 |
| 2 | Design 2 | 25 |
| 3 | Design 3 | 25 |
The class Exadsrcise\Domain\Promotion\PromotionSelector was created to abstract the promotion selection based on its percentage.
use Exadsrcise\Domain\Promotion\PromotionSelector;
use Exadsrcise\Model\Promotion;
$promotionPicker = new PromotionSelector();
$promotionPicker->pushPromotion(new Promotion("Design no. 1", 50));
$promotionPicker->pushPromotion(new Promotion("Design no. 2", 25));
$promotionPicker->pushPromotion(new Promotion("Design no. 3", 25));
$selected = $promotionPicker->pickOne(); // Will return the selected item.
// Developer can actually 'force' a minimum percentage to filter.
// Just pass the minimum required percentage value
$selectedForPremium = $promotionPicker->pickOne(50); // Design no. 1 will always return hereThe solution has performance improved, since we only iterate one time trough all promotion list.
This application contains all solved exercises. However, there are some missing features that were ignored in order to focus on the solution.
Use a different approach to register dependencies (such as Database or even the Commands) on the boot of the application. This way, we can divide responsability of those features' lifecycle, allow dependency injection trough constructor (SOLID best practices), etc. Some cool packages that already helps this approach:
This solution doesn't have any code coverage. There was my intention to provide that (at least Unit test coverage), but once again it was not requested as part of the exercise, so this Application only provides the solution of it.
All the output of the commands are done in the command itself.