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HELLO - Start Building Your Own ORM

Use PHP to reshape the kinds of objects coming from a SQL database

Learning Objectives

Learn about the challenges of converting SQL rows into JSON
Practice using PHP to reshape objects
etc.

Prerequisites

Experience with RESTful routes
Basic PHP
Familiarity with JSON
Familiarity with SQL

Getting Started

You'll be working in one PHP file, and building out your answers as you work through this hw.

Deliverables

Technical Requirements

Must run without syntax errors (comment out code that doesn't work and add comments)
Must complete parts 1 - 6

Submission Guidelines

Must be submitted no later than before the start of next class

Context

The founder of the start-up H.E.L.L.O (Housing Elite Leveraged Location Organization) wants you to help launch her amazing idea.

Too many college graduates these days have too high loans to pay back. This is preventing them from being able to get into premium housing locations, where everything is in walking distance and work is a sweet sweet short commute away.

One night, our brilliant entrepreneur was reminiscing about how much she enjoyed living in a dorm and thought, why can't people keep on living in a dorm?

And thus H.E.L.L.O. was founded. A premier housing solution. For the low low starting price of $3999 a month for a bunk bed shared with one other person and a co-ed bathroom shared by everyone on the same floor, anyone's housing dreams can come true!

H.E.L.L.O already has funding for one location!

Your first task is to help build a tenant tracker.

Part 1 - explanation

SQL stores data in rows and columns, so in order to get the data to display on a web page, we need to convert the data from rows and columns into associative arrays with keys and values. Fortunately, PHP does this for us, but we need to do some manual coding to get it to work exactly as we want it to.

If we just have one table with the following keys and values:

name	age	home_id
Chase	30	1

PHP can turn this into an associative array which would look something like this:

[
    [
        "name" => "Chase",
        "age" => "30",
        "home_id" => "1"
    ]
]

Remember, that PHP doesn't allow us to spontaneously create an object with any arbitrary properties that we want like JavaScript does. We can use associative in this manner, though. It's a good way to keep track of a data structure that requires key/value pairs.

If we had more than one person...

name	age	home_id
Chase	30	1
Gert	23	1

PHP will give us something like this:

[
    [
        "name" => "Chase",
        "age" => "30",
        "home_id" => "1"
    ],
    [
        "name" => "Gert",
        "age" => "23",
        "home_id" => "1"
    ]
]

This is straightforward. However, we start to get a few wrinkles once we start joining tables. In this homework's situation, our location HAS MANY people (and each person HAS ONE location). This is also called a ONE to MANY relationship. If we were to join Chase's info with his location's info, our table could look like the following:

name	age	home_id	home_street	home_city	home_state	home_zip_code
Chase	30	1	"1600 Broadway"	"New York"	"NY"	10019

PHP would turn this all this info into just one associative array:

Original Format

[
    [
        "name"=>"Chase",
        "age"=>"30",
        "home_id"=>"1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=>"10019"
    ]
]

But what we really want is to change the shape of the data and have home as a nested associative array. We'd also want to convert our numbers back into numbers from strings:

New Format

[
    "name"=>"Chase",
    "age"=>30,
    "home"=> [
        "id"=> 1,
        "street"=>"1600 Broadway",
        "city"=>"New York",
        "state"=>"NY",
        "zip_code"=> 10019
    ]
]

This might seem relatively minor, but it makes more sense to store the data this way. It's much more representative of the real world.

Part 2 - code along

First, let's define a new function dataTransform. It will take a single associative array inside of an indexed array called person_array:

function dataTransform($person_array){

}

Now let's create a fake $people array, containing a single associative array that represents one person. This $people array is similar to what PHP will give us after it retrieves data from Postgres. In reality, the $people array would contain multiple people (associative arrays), but for now let's just put one in. Next, call dataTransform and pass that "fake" $people array in as a parameter:

$people = [
    [
        "name"=>"Chase",
        "age"=>"30",
        "home_id"=>"1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=>"10019"
    ]
];

function dataTransform($person_array){

}

dataTransform($people);

Second, inside of dataTransform, let's return an empty associative array called $person:

function dataTransform($person_array){
    $person = [];
    return $person;
}

Set the result of dataTransform($people); to a variable and then var_dump() it:

$result = dataTransform($people);
var_dump($result);

We can make whatever keys we want for our new object:

function dataTransform($person_array){
    $person = [
        "name" => "Chase",
        "age" => "30"
    ];
    return $person;
}

And we can ALMOST place our values from our $person_array into our new hash

function dataTransform($person_array){
    $person = [
        "name" => $person_array["name"],
        "age" => $person_array["age"]
    ];
    return $person;
}

Check it! This won't quite work because our $person_array is an associative array inside an indexed array (remember, $person_array will eventually contain multiple people). We can easily take the associative array out of the indexed array though:

function dataTransform($person_array){
    $first_person = $person_array[0];
    $person = [
        "name" => $first_person["name"],
        "age" => $first_person["age"]
    ];
    return $person;
}

Now try again! The full code:

$people = [
    [
        "name"=>"Chase",
        "age"=>"30",
        "home_id"=>"1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=>"10019"
    ]
];

function dataTransform($person_array){
    $first_person = $person_array[0];
    $person = [
        "name" => $first_person["name"],
        "age" => $first_person["age"]
    ];
    return $person;
}

$result = dataTransform($people);
var_dump($result);

This should print a single associative array containing just the name and the age of the person:

array(2) {
  ["name"]=>
  string(5) "Chase"
  ["age"]=>
  string(2) "30"
}

It ALMOST matches the New Format, but the age is a string. We can use a special PHP function called intval() to fix that:

$person = [
    "name" => $first_person["name"],
    "age" => intval($first_person["age"])
];

Check it again!

array(2) {
  ["name"]=>
  string(5) "Chase"
  ["age"]=>
  int(30)
}

Part 3 - build it

Don't forget, we want our dataTransform function to return an object that also includes the other information about our person.

[
    "name"=>"Chase",
    "age"=>30,
    "home"=> [
        "id"=> 1,
        "street"=>"1600 Broadway",
        "city"=>"New York",
        "state"=>"NY",
        "zip_code"=> 10019
    ]
]

How do we get that nested home associative array in the results?

Part 4 - build it

As we get new clients, not all of them will have a home right away. We need to add a way to check if a person has a home address, and if that's the case, return the reshaped associative array else just return the name and age properties like we did in part 2.

Don't forget to test it with something like this:

$people = [
    [
        "name"=>"Chase",
        "age"=>"30",
        "home_id"=>"1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=>"10019"
    ]
];

$result = dataTransform($people);
var_dump($result);

$people2 = [
    [
        "name" => "Gert",
        "age" => "23"
    ]
];

$result2 = dataTransform($people2);
var_dump($result2);

Part 5 - build it

HELLO already has three tenants! Converting each object's format one by one is a drag. Update dataTransform so that it converts an array of many people into the New Format shape:

Original Format

$people = [
    [
        "name"=>"Gert",
        "age"=>"23",
        "home_id"=> "1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=> "10019"
    ],
    [
        "name"=>"Alex",
        "age"=>"42",
        "home_id"=> "1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=> "10019"
    ],
    [
        "name"=>"Nico",
        "age"=>"61"
    ]
];

Check yourself: does your method still work if a person doesn't yet have a home address?

New Format

[
    [
        "name"=>"Gert",
        "age"=>23,
        "home"=> [
          "id"=> 1,
          "street"=>"1600 Broadway",
          "city"=>"New York",
          "state"=>"NY",
          "zip_code"=> 10019
        ]
    ],
    [
        "name"=>"Alex",
        "age"=>42,
        "home"=> [
          "id"=> 1,
          "street"=>"1600 Broadway",
          "city"=>"New York",
          "state"=>"NY",
          "zip_code"=> 10019
        ]
    ],
    [
        "name"=>"Nico",
        "age"=> 61
    ]
]

Part 6

For this part, write a brand new dataTransformLocations method. Save your previous one(s)

HELLO is growing rapidly and has acquired an amazing high profile space for their next luxury dorm experience. So next, we'd like to be able to show a list of all our addresses with their corresponding tenants:

Original Format

NOTE assume all people with home_id of 1 are next to each other in the array. Same with home_id of 2, 3, etc

$people = [
    [
        "name"=>"Gert",
        "age"=>"23",
        "home_id"=> "1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=> "10019"
    ],
    [
        "name"=>"Alex",
        "age"=>"42",
        "home_id"=> "1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=> "10019"
    ],
    [
        "name"=>"Nico",
        "age"=>"61",
        "home_id"=> "1",
        "home_street"=>"1600 Broadway",
        "home_city"=>"New York",
        "home_state"=>"NY",
        "home_zip_code"=> "10019"
    ],
    [
        "name"=>"Molly",
        "age"=>"55",
        "home_id"=> "2",
        "home_street"=>"1 Alcatraz Island",
        "home_city"=>"San Francisco",
        "home_state"=>"CA",
        "home_zip_code"=> "94133"
    ],
    [
        "name"=>"Karolina",
        "age"=>"82",
        "home_id"=> "2",
        "home_street"=>"1 Alcatraz Island",
        "home_city"=>"San Francisco",
        "home_state"=>"CA",
        "home_zip_code"=> "94133"
    ]
];

New Format

[
    [
        "id"=> 1,
        "street"=>"1600 Broadway",
        "city"=>"New York",
        "state"=>"NY",
        "zip_code"=> 10019,
        "tenants" => [
            [
                "name"=>"Gert",
                "age"=>23
            ],
            [
                "name"=>"Alex",
                "age"=>42
            ],
            [
                "name"=>"Nico",
                "age"=>61
            ]
        ]
    ],
    [
        "id"=> 2,
        "street"=>"1 Alcatraz Island",
        "city"=>"San Francisco",
        "state"=>"CA",
        "zip_code"=> 94133,
        "tenants" => [
            [
                "name"=>"Molly",
                "age"=>23
            ],
            [
                "name"=>"Karolina",
                "age"=>42
            ]
        ]
    ]
]

Part 7 - Hungry for more

Create the ability for dataTransformLocations to optionally return a specific home (with its tenants), based on an optional second home_id param:

$result = dataTransform($people, 2);

should return

[
    "id"=> 2,
    "street"=>"1 Alcatraz Island",
    "city"=>"San Francisco",
    "state"=>"CA",
    "zip_code"=> 94133,
    "tenants" => [
        [
            "name"=>"Molly",
            "age"=>23
        ],
        [
            "name"=>"Karolina",
            "age"=>42
        ]
    ]
]

You did it! You started building your own ORM (Object Relational Mapping)

13 KiB Raw Permalink Blame History

HELLO - Start Building Your Own ORM

Learning Objectives

Prerequisites

Getting Started

Deliverables

Technical Requirements

Submission Guidelines

Context

Part 1 - explanation

Part 2 - code along

Part 3 - build it

Part 4 - build it

Part 5 - build it

Original Format

New Format

Part 6

Original Format

New Format

Part 7 - Hungry for more

13 KiB

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