seeder.php

<?php

class Random
{

	public static function distributed($elements)
	{

		if (array_sum($elements) !== 100) {
			throw new \Exception('randomWithDistribution: sum of probabilities must be 100');
		}

		$random = rand(1, 100);
		$tot = 0;

		foreach ($elements as $id => $weight) {
			$tot += $weight;
			if ($random <= $tot) {
				return $id;
			}
		}
	}
}

abstract class RandomType
{

	protected array $settings;

	function __construct(array $settings)
	{
		$this->settings = $settings;
	}

	abstract function craft(array $record);
}

class FallbackType extends RandomType
{

	public function craft(array $record)
	{
		return  $this->settings['name'] . ' is not implemented';
	}
}

class RangeType extends RandomType
{

	public function craft(array $record)
	{
		$min = $this->settings[1][0];
		$max = $this->settings[1][1];

		return rand($min, $max);
	}
}

class OptionType extends RandomType
{

	public function craft(array $record)
	{
		$entries = $this->settings[1];
		return $entries[mt_rand(0, count($entries) - 1)];
	}
}

class WeightedOptionType extends RandomType
{

	public function craft(array $record)
	{
		return Random::distributed($this->settings[1]);
	}
}

class DateType extends RandomType
{

	public function craft(array $record)
	{
		$min = strtotime($this->settings[1][0]);
		$max = strtotime($this->settings[1][1]);
		$time = mt_rand($min, $max);

		return (new \DateTime())->setTimestamp($time);
	}
}

class CustomType extends RandomType
{

	public function craft(array $record)
	{
		$closure = $this->settings[1];
		return $closure($record);
	}
}

class Seeder
{

	public static function seed(int $qty, array $rules, Closure $onGenerated): void
	{
		$generators = self::getGenerators($rules);

		for ($i = 1; $i <= $qty; $i++) {

			$record = ['__id__' => $i];

			foreach ($generators as $field => $g) {
				$record[$field] = $g->craft($record);
			}

			$onGenerated($record);
		}
	}

	private static function getGenerators(array $rules): array
	{
		$generators = [];

		foreach ($rules as $field => $rule) {
			$generators[$field] = self::instantiateGenerator($rule);
		}

		return $generators;
	}

	private static function instantiateGenerator(array $rule): RandomType
	{
		$generatorName = ucfirst($rule[0]) . 'Type';

		if (!class_exists($generatorName)) {
			return new FallbackType(['name' => $rule[0]]);
		}

		return new $generatorName($rule);
	}
}

/*
	Usage
 */

$output_file = fopen('output.sql', 'w');

Seeder::seed(40000, [
	'status' => ['option', ['a']],
	'cycle' => ['WeightedOption', ['d' => 97, 'm' => 3]],
	'grouping' => ['range', [0, 2]],
	'fiscal_id' => ['range', [1, 2000]],
	'start' => ['date', ['2021-01-01 00:00:00', '2021-12-31 00:00:00']],
	'end' => ['custom', function ($record) {
		$end = clone $record['start'];
		return $end->modify($record['cycle'] == 'm' ? '+ 1 month' : '+ 1 day');
	}],
], function (array $record) use($output_file) {
	$query ='insert into myTable (status, cycle, grouping, fiscal_id, start, end) values '
		. sprintf(
			"('%s', '%s', %d, %d, '%s', '%s');\r\n",
			$record['status'],
			$record['cycle'],
			$record['grouping'],
			$record['fiscal_id'],
			$record['start']->format('Y-m-d'),
			$record['end']->format('Y-m-d')
		);

	//echo $query . "<br />";
	fwrite($output_file, $query);
});

fclose($output_file);