PHP - Playing with Records - Part Two

   
   
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Article Series

This article series discuss more than 30 different programming languages. Please read overview before you read any of the details.

Playing with Records Related Articles.

Table of Content
Where to Discuss?

Local Group

Preface

Goal: Learning PHP without HTML burden.

Preface

Goal: Continue Part One

4: Data Structure Using Class

Simply tidier.

There is other alternative data structure as well. Instead of Associative Array, we can use Class.

Class

The declaration is simple.

<?php
class MySong {
  public function __construct(
    public String $title = "",
    public Array  $tags  = []
  ) {}
}

$song = new MySong(
  'Cantaloupe Island',
  ['60s', 'jazz']
);

var_export($song);

__

WWe can examine the object shown in output result below:

❯ php 12-record-a.php
MySong::__set_state(array(
   'title' => 'Cantaloupe Island',
   'tags' => 
  array (
    0 => '60s',
    1 => 'jazz',
  ),
))

If you prefer shorter output you can utilize this code below:

<?php
printf("%s: [%s]\n",
  $song->title,
  join(', ', $song->tags));

With the result as below:

❯ php 12-record-b.php
Cantaloupe Island: [60s, jazz]

PHP: Displaying Class Properties

The Songs Structure

We can continue our journey to records using Class. A little bit complex, but worth it.

<?php
class MySong {
  public function __construct(
    public String $title = "",
    public Array  $tags  = []
  ) {}
}

$songs = [
  new MySong(
    'Cantaloupe Island', ['60s', 'jazz']),
  new MySong('Let It Be', ['60s', 'rock']),
  new MySong(
    'Knockin\' on Heaven\'s Door',
    ['70s', 'rock']),
  new MySong('Emotion', ['70s', 'pop']),
  new MySong('The River'),
];

foreach($songs as $song) {
  printf("%s: [%s]\n",
    $song->title,
    join(', ', $song->tags));
}

__

With the result similar as below record:

❯ php 13-songs.php
Cantaloupe Island: [60s, jazz]
Let It Be: [60s, rock]
Knockin' on Heaven's Door: [70s, rock]
Emotion: [70s, pop]
The River: []

[]

5: Separating Module

Again, we need to reuse the songs record multiple times, so we separate the record structure from logic.

Songs Module

The code can be shown as below:

<?php
class MySong {
  public function __construct(
    public String $title = "",
    public Array  $tags  = []
  ) {}
}

$songs = [
  new MySong(
    'Cantaloupe Island', ['60s', 'jazz']),
  new MySong('Let It Be', ['60s', 'rock']),
  new MySong(
    'Knockin\' on Heaven\'s Door',
    ['70s', 'rock']),
  new MySong('Emotion', ['70s', 'pop']),
  new MySong('The River'),
];

__

PHP: The Songs Module Containing array of Class

Using Songs Module

Now we can have a very short code.

<?php
require_once(__DIR__.'/MyClassSongs.php');

foreach($songs as $song) {
  printf("%s: [%s]\n",
    $song->title,
    join(', ', $song->tags));
}

With the result, as below. Exactly the same as previous output result.

PHP: Using Songs Module

❯ php 14-module.php
Cantaloupe Island: [60s, jazz]
Let It Be: [60s, rock]
Knockin' on Heaven's Door: [70s, rock]
Emotion: [70s, pop]
The River: []

[]

3: Finishing The Task

Extract, Flatten, Unique

Extracting Class

Using arrow to access property

<?php
require_once(__DIR__.'/MyClassSongs.php');

$tagss = array_map(
  function ($song) { return $song->tags; },
  $songs);

printf("%s\n", json_encode($tagss));

With the result is, still array of array as shown below.

❯ php 15-extract.php
[["60s","jazz"],["60s","rock"],["70s","rock"],["70s","pop"],[]]

You can see thw we are uing [] instead of nil.

PHP: Extracting Dictionary

Flatten

We still have to flatten, the multi dimensional array, with this ... feature.

<?php
require_once(__DIR__.'/MyClassSongs.php');

$tagss = array_map(
  function ($song) { return $song->tags; },
  $songs);

$tags = array_merge(...$tagss);

printf("%s\n", json_encode($tags));

With the result is, still array of array as shown below.

❯ php 16-flatten.php
["60s","jazz","60s","rock","70s","rock","70s","pop"]

PHP: Flattening Array

Unique

Advance List Comprehension

Finally we solve unique list, after flattening.

<?php
require_once(__DIR__.'/MyClassSongs.php');

$tags =
  array_values(
    array_unique(
      array_merge(
        ... array_map(
          function ($song) {
            return $song->tags; },
          $songs)
  )));

printf("%s\n", json_encode($tags));

With the result similar as below array:

❯ php 17-unique.php
["60s","jazz","rock","70s","pop"]

PHP: Solving Unique Song

Good enough.

What is Next 🤔?

We have alternative way to do get unique list. And we will also discuss about concurrency.

Consider continue reading [ PHP - Playing with Records - Part Three ].