Dynamically create MySQL table columns - php

Question

I have the following MySQL table which is structured like that:
| id | bonus0 |
Now I want to add the following data set:
| id | bonus0 | bonus1 | bonus2 | bonus3 |
| 10 | 4582 | 2552 | 8945 | 7564 |
As you can see the columns bonus1 - bonus3 aren´t created yet.
How would a php script/ query look like which checks if enough columns are already available and if not which will create the missing ones with consecutive numbers at the end of the word "bonus"?
So in the example the columns bonus1 - bonus3 would be created automatically by the script.

Answer 1

In reality (I mean a normalized relational database) you should have 3 tables. Lets call them people, bonuses and bonus_to_person
people looks like:
+-----------------+------------+
| person_id | name |
+_________________+____________+
| 1 | john |
+-----------------+------------+
| 2 | frank |
+-----------------+------------+
bonuses Looks like
+----------------+--------------+
| bonus_id | amount |
+________________+______________+
| 1 | 1000 |
+----------------+--------------+
| 2 | 1150 |
+----------------+--------------+
| 3 | 1200 |
+----------------+--------------+
| 4 | 900 |
+----------------+--------------+
| 5 | 150 |
+----------------+--------------+
| 6 | 200 |
+----------------+--------------+
bonus_to_person Looks like
+----------------+-----------------+
| bonus_id | person_id |
+________________+_________________+
| 1 | 1 |
+----------------+-----------------+
| 2 | 2 |
+----------------+-----------------+
| 3 | 2 |
+----------------+-----------------+
| 4 | 1 |
+----------------+-----------------+
| 5 | 1 |
+----------------+-----------------+
| 6 | 1 |
+----------------+-----------------+
This way, any ONE person can have unlimited bonuses simply by INSERTING into bonuses with the amount, and INSERTING into bonus_to_person with the bonus_id and person_id
The retrieval of this data would look like
SELECT a.name, c.amount from people a
LEFT JOIN bonus_to_people b
ON a.person_id = b.person_id
LEFT JOIN bonuses c
ON c.bonus_id = b.bonus_id
WHERE a.person.id = 1;
Your result from something like this would look like
+------------+----+-------+
| name | amount |
+____________+____________+
| john | 1000 |
+------------+------------+
| john | 900 |
+------------+------------+
| john | 150 |
+------------+------------+
| john | 200 |
+------------+------------+
You should be using this normalized approach for any database that will continue growing -- Growing "deeper" than "wider" is better in your case ..

Answer 2

// Get existing columns of the table
// $queryResult = run SQL query using PDO/mysqli/your favorite thing: SHOW COLUMNS FROM `table`
// Specify wanted columns
$search = ['bonus0', 'bonus1', 'bonus2', 'bonus3'];
// Get just the field names from the resultset
$fields = array_column($queryResult, 'Field');
// Find what's missing
$missing = array_diff($search, $fields);
// Add missing columns to the table
foreach ($missing as $field) {
// Run SQL query: ALTER TABLE `table` ADD COLUMN $field INT
}