immigrateData.php

<?php
class db_handler extends PDO
{
	private function emitError($message)
	{
		return $message;
	}

	public function immigrateData(
		$table_from, $columns_from, $table_to, $mapping, $start_at = 0, $limit = null
	)
	{
		$page_amount = 1000;
		if(!is_array($columns_from) && $columns_from !== '*') {
			return $this->emitError(
				'Columns in the origin table are not properly supplied.'
			);
		}
		if(count($mapping) === 0) {
			return $this->emitError(
				'The mapping rules are empty.'
			);
		}
		if($page_amount <= 0) {
			return $this->emitError(
				'Set a proper amount for a page of rows.'
			);
		}
		$count_done = 0;

		if(!is_null($limit)) {
			$total_rows = $limit;
		} else {
			$total_rows = $this->query("select count(*) from $table_from");
			$total_rows = $total_rows->fetchColumn();
			if ($total_rows == 0) {
				return $this->emitError(
					'No rows were found in the origin table.'
				);
			}
		}

		$query = 'select '.
			((is_array($columns_from) && count($columns_from))?
				implode($columns_from, ', '):
				$columns_from).
			" from $table_from";
		for(
			$start_at;
			$start_at < $total_rows;
		) {
			$query_to_submit = '';
			$amount_to_read = min($total_rows-$start_at, $page_amount);
			$page = $this->query("$query limit $start_at, $amount_to_read");
			$start_at += $amount_to_read;
			foreach($page as $row) {
				$cells = implode(
						array_map(function ($column_name) use ($mapping, $row) {
							$cell = $mapping[$column_name]($row);
							if (strtoupper($cell) !== 'NULL')
								$cell = "'$cell'";
							return $cell;
						}, array_keys($mapping)),
						', '
					);

				$query_to_submit .= "insert into $table_to".
					(count($mapping)?
						'('.implode(array_keys($mapping), ' ,').') ':
						' ' ).
					'values('.
					$cells.
					");\n";
			}

			try {
				$count_done += (int)($this->exec($query_to_submit));
			} catch (PDOException $e) {
				return $this->emitError($e->getMessage());
			}
		}

		return $count_done;
	}
}

mappingExample.php

<?php
$mapping[161] = array(
	'delflag' => function($v) {return is_null($v['deleteID'])?0:1;},
	'uid' => function($v) {return $v['userID'];},
	'upw' => function($v) {return $v['passwd'];},
	'uname' => function($v) {return $v['userNM'];},
	'subject' => function($v) {
		return filter_var($v['titleDS'], FILTER_SANITIZE_MAGIC_QUOTES);},
	'memo' => function($v) {
		return filter_var($v['memoDS'], FILTER_SANITIZE_MAGIC_QUOTES);},
	'view' => function($v) {return $v['readCount'];},
	'writetime' => function ($v) {
		return is_null($v['insertDT']) ? 'NULL' : str_replace(
			'/', '-',
			"{$v['insertDT']} {$v['insertTM']}"
		);
	},
	'updatetime' => function ($v) {
		return is_null($v['updateDT']) ? 'NULL' : str_replace(
			'/', '-',
			"{$v['updateDT']} {$v['updateTM']}"
		);
	},
	'isimportant' => function($v) {return $v['noticeTP'] == 0? 0: 1;},
	'issecret' => function($v) {return $v['secretTP'] == 'Y'? 1: 0;},
	'category' => function($v) {return $v['categoryID'];},
	'hmode' => function($v) {return $v['htmlTP'] == 'Y'? 2: 0;}
);