class test1
{
	//単体の連想配列のデータ
	function test1()
	{
		$data=[
			'name' => "tanaka",
			'class' => 1,
		];
		echo "data count:".count($data).PHP_EOL;//data count:2
		echo "data.name:".$data["name"].PHP_EOL;//data.name:tanaka
		echo "data.class:".$data["class"].PHP_EOL;//data.class:1
		$this->changeArray($data, "class", 2);
		echo "data.class:".$data["class"].PHP_EOL;//data.class:2
		$this->deleteFieldArray1($data, "name");
		echo "data count:".count($data).PHP_EOL;//data count:1
		$this->foreachArray($data);
		//foreachの結果
		//class: 2

		$this->addArray($data, "age", 20);
		//foreachの結果
		//class: 2
		//age: 20

		$this->forTest1($data);
		//[結果]
		//class: 2
		//age: 20

		$this->forTest2($data);
		//[結果]
		//class: 2
		//age: 20

		$this->deleteFieldArray2($data, "class");
		$this->foreachArray($data);
		//foreachの結果
		//age: 20

		$this->deleteFieldArray2($data, "age");
		$this->foreachArray($data);
		//foreachの結果
		//データがなくなったため何も表示されません
		echo "data count:".count($data).PHP_EOL;//data count:0
	}
	//foreachを使った配列を読み込む方法
	private function foreachArray(array $ary)
	{
		echo "foreachArray".PHP_EOL;
		foreach ($ary as $key => $value) 
		{
			echo $key . ': ' . $value . PHP_EOL;
		}
	}
	//指定のキーを変更
	private function changeArray(array &$ary, string $key, int $value)
	{
		$ary[$key] = $value;
	}
	//指定のキーを削除(unsetを使用)
	private function deleteFieldArray1(array &$ary, string $key)
	{
		unset($ary[$key]);
	}
	//指定のキーを削除(array_diff_keyを使用)
	private function deleteFieldArray2(array &$ary, string $key)
	{
		// 削除したいキーのリストを新しい配列として定義
		$keys_to_remove = [$key];
		
		// array_diff_key() は、第1引数の配列から第2引数に含まれるキーを取り除いた結果を返します
		$ary = array_diff_key($ary, array_flip($keys_to_remove));
	}
	//指定のキーを削除(array_filterを使用)
	private function deleteFieldArray3(array &$ary, string $removeKey)
	{
		$ary = array_filter(
			$ary,
			function ($key) use ($removeKey) {
				// 削除したいキーと一致しなければTRUE（残す）を返す
				return $key !== $removeKey;
			},
			ARRAY_FILTER_USE_KEY // キーを使ってフィルタリングするフラグ
		);

	}
	//データを追加
	private function addArray(array &$ary, string $key, int $value)
	{
		$ary[$key] = $value;
	}
	//配列の内部ポインタを操作しながらループします
	//reset() と next() を使います
	//可読性が低く、バグの原因になりやすいため、実務ではおすすめしません。
	private function forTest1(array $ary)
	{
		// ポインタを最初の要素にリセット
		reset($ary);
		
		// current()がfalse（またはnull, 0など）でない限りループを続行
		for ($i = 0; current($ary) !== false; next($ary), $i++) 
		{
			$key = key($ary);
			$value = current($ary);
			echo $key . ": " . $value . PHP_EOL;
		}
	}
	//array_keys() ですべてのキーを取得してからループします
	//キーのリストを取得し、それをインデックス配列として for ループで回します。
	private function forTest2(array $ary)
	{
		// すべてのキーを配列として取得
		$keys = array_keys($ary);
		$count = count($keys);
		
		for ($i = 0; $i < $count; $i++) 
		{
			$key = $keys[$i];
			$value = $ary[$key];
			echo $key . ": " . $value . PHP_EOL;
		}
	}
}
echo "<pre>";
$cls1= new test1();
$cls1->test1();
echo "</pre>";

class test1
{
	//Data of a single associative array
	function test1()
	{
		$data=[
		'name' => "tanaka",
		'class' => 1,
		];
		echo "data count:".count($data).PHP_EOL;//data count:2
		echo "data.name:".$data["name"].PHP_EOL;//data.name:tanaka
		echo "data.class:".$data["class"].PHP_EOL;//data.class:1
		$this->changeArray($data, "class", 2);
		echo "data.class:".$data["class"].PHP_EOL;//data.class:2
		$this->deleteFieldArray1($data, "name");
		echo "data count:".count($data).PHP_EOL;//data count:1
		$this->foreachArray($data);
		//Result of foreach
		//class: 2
		
		$this->addArray($data, "age", 20);
		//Result of foreach
		//Class: 2
		//Age: 20
		
		$this->forTest1($data);
		//[Result]
		//Class: 2
		//Age: 20
		
		$this->forTest2($data);
		//[Result]
		//Class: 2
		//Age: 20
		
		$this->deleteFieldArray2($data, "class");
		$this->foreachArray($data);
		//Result of foreach
		//Age: 20
		
		$this->deleteFieldArray2($data, "age");
		$this->foreachArray($data);
		//Result of foreach
		//Nothing is displayed because there is no more data.
		echo "data count:".count($data).PHP_EOL;//data count:0
	}
	//How to read an array using foreach
	private function foreachArray(array $ary)
	{
		echo "foreachArray".PHP_EOL;
		foreach ($ary as $key => $value)
		{
		echo $key . ': ' . $value . PHP_EOL;
		}
	}
	// Change the specified key
	private function changeArray(array &$ary, string $key, int $value)
	{
		$ary[$key] = $value;
	}
	// Delete the specified key (using unset)
	private function deleteFieldArray1(array &$ary, string $key)
	{
		unset($ary[$key]);
	}
	// Delete the specified key (using array_diff_key)
	private function deleteFieldArray2(array &$ary, string $key)
	{
		// Define a new array containing the list of keys to delete
		$keys_to_remove = [$key];
		
		// array_diff_key() returns the result of removing the keys in the second argument from the array in the first argument
		$ary = array_diff_key($ary, array_flip($keys_to_remove));
	}
	// Delete the specified key (using array_filter)
	private function deleteFieldArray3(array &$ary, string $removeKey)
	{
		$ary = array_filter(
		$ary,
		function ($key) use ($removeKey) {
		// Return TRUE (keep) if the key does not match the key to be deleted.
		return $key !== $removeKey;
	},
	ARRAY_FILTER_USE_KEY // Flag to filter using the key.
	);
	
	}
	// Add data.
	private function addArray(array &$ary, string $key, int $value)
	{
		$ary[$key] = $value;
	}
	// Loop while manipulating the array's internal pointer.
	// Use reset() and next().
	// Not recommended for practical use due to poor readability and prone to bugs.
	private function forTest1(array $ary)
	{
		// Reset the pointer to the first element
		reset($ary);
		
		// Continue looping unless current() is false (or null, 0, etc.)
		for ($i = 0; current($ary) !== false; next($ary), $i++)
		{
			$key = key($ary);
			$value = current($ary);
			echo $key . ": " . $value . PHP_EOL;
		}
	}
	// Get all keys with array_keys(), then loop
	// Get a list of keys and use it as an index array in a for loop.
	private function forTest2(array $ary)
	{
		// Get all keys as an array
		$keys = array_keys($ary);
		$count = count($keys);
		
		for ($i = 0; $i < $count; $i++)
		{
			$key = $keys[$i];
			$value = $ary[$key];
			echo $key . ": " . $value . PHP_EOL;
		}
	}
}
echo "<pre>";
$cls1 = new test1();
$cls1->test1();
echo "</pre>";