This example shows how to use the 'split' TypoScript function to create a set of checkboxes easily. There are three files total: general code, stdWrap helper and usage example.

checkboxes.txt

temp.checkbox_with_split = COA
temp.checkbox_with_split {

	# Define data
	10 = LOAD_REGISTER
	10 {
		# Valid bits in the field
		bits = 1,2,3,4,5,6,7

		# Field name in the database. Don't move below other registers!
		fieldName = tx_myext_field
	}

	# Split bit values and creates checkboxes for them.
	20 = TEXT
	20 {
		data = register:bits
		split {
			token = ,
			cObjNum = 1

			# Checkbox
			1 = COA
			1 {
				# Prepare data
				10 = LOAD_REGISTER
				10 {
					# Bit in the database field (just incrementing for each checkbox)
					bit.current = 1

					# "checked" attribute of the checkbox
					checkedAttr =
					checkedAttr.override = checked="checked"
					checkedAttr.override {
						if.isTrue {
							postUserFunc = tx_myext_stdwrap->checkBitValue
							postUserFunc {
								# Bits are counted from 1!
								bit.data = register:bit
								fieldName.data = register:fieldName
							}
						}
					}

					# Label text of the checkbox
					label {
						stdWrap {
							dataWrap = LLL:EXT:myext/locallang_db.xml:tx_mytable.{register:fieldName}.{register:bit}
							wrap3 = {|}
							insertData = 1
						}
						htmlSpecialChars = 1
					}
				}

				# Field
				20 = TEXT
				20 {
					# Assemble the checkbox from registers
					dataWrap = <input {register:checkedAttr} id="{register:fieldName}_{register:bit}" name="tx_mext_pi1[{register:fieldName}][]" type="checkbox" value="{register:bit}" /><label for="{register:fieldName}_{register:bit}">{register:label}</label><br />
				}

				100 = RESTORE_REGISTER
			}
		}
	}
}

class.tx_myext_stdwrap.php

<?php
/**
 * This class contains a postUserFunc functions for the stdWrap.
 *
 * (c) 2013 Dmitry Dulepov
 *
 * @author Dmitry Dulepov <dmitry.dulepov@gmail.com>
 */
class tx_myext_stdwrap implements t3lib_Singleton {

	/** @var tslib_cObj */
	public $cObj;

	/**
	 * Cheks that the value of the bit 'bit' in the field 'fieldName' matches.
	 *
	 * @param string $content
	 * @param array $conf
	 * @return string
	 */
	public function checkBitValue($content, array $conf) {
		if (isset($conf['bit.'])) {
			$conf['bit'] = $this->cObj->stdWrap($conf['bit'], $conf['bit.']);
		}
		if (isset($conf['fieldName.'])) {
			$conf['fieldName'] = $this->cObj->stdWrap($conf['fieldName'], $conf['fieldName.']);
		}

		$bit = 1 << max(0, intval($conf['bit']) - 1);
		$fieldValue = intval($this->cObj->data[$conf['fieldName']]);

		return ($fieldValue & $bit);
	}

}

usage-example.txt

<INCLUDE_TYPOSCRIPT: source="FILE:EXT:myext/static/includes/checkboxes.txt">

plugin.tx_myext_pi1 {

	rendering.checkboxes = COA
	rendering.checkboxes {
		20 < rendering.checkboxes
		20 {
			20.data = LLL:EXT:myext/locallang_db.xml:tx_mytable.tx_myext_field2
			30.10 {
				bits = 1,2,3,4,5
				fieldName = tx_myext_field2
			}
		}

		30 < rendering.checkboxes
		30 {
			20.data = LLL:EXT:myext/locallang_db.xml:tx_mytable.tx_myext_field3
			30.10 {
				bits = 1,2
				fieldName = tx_myext_field3
			}
		}
	}
}