string-to-array.php

<?php
/**
 * Create an array from a hyphenated, newline separated string.
 *
 * Converts a string like:
 *
 * Tacos
 * Hamburger
 * - With cheese
 * -- Cheddar
 * -- Gouda
 * - With bacon
 * Sandwich
 * - With ham
 * Hot dog
 * Pizza
 *
 * To:
 *
 * array(
 *    'Tacos' => 'Tacos',
 *    'Hamburger' => array(
 *       'With cheese' => array(
 *          'Cheddar' => 'Cheddar',
 *          'Gouda' => 'Gouda',
 *       ),
 *       'With bacon' => 'With bacon'
 *    ),
 *    'Sandwich' => array(
 *       'With ham' => 'With ham'
 *    ),
 *    'Hot dog' => 'Hot dog',
 *    'Pizza' => 'Pizza'
 * )
 *
 * In addition to hyphens, em- and en-dashes count as level indicators.
 *
 * @param string $string To process.
 * @param int $level Current array level. Intended to be used recursively by
 *    the function, but can also be used to flatten the structure x levels.
 * @return array
 */
function string_to_array( $string, $level = 0 ) {
	$level++;

	// Newline NOT followed by a number of dashes, depending on current level.
	// This will items followed by sub items in the same string, until they
	// are split recursively on the next level.
	$newline_split_regex = "/\R+(?![\—\–\-]{{$level}})/";
	$clean_dashes_regex = '/^[\—\–\-\s]+/';

	$array = preg_split( $newline_split_regex, trim( $string ) );
	$return = array();

	foreach ( $array as $value ) :
		$value = trim( $value );

		// If there are newlines in the item, we have sub items
		if ( preg_match( '/\R/', $value ) ) :

			// Split on first newline to get the sub items parent...
			$sub_items = preg_split( '/\R+/', $value, 2 );
			$sub_key = preg_replace( $clean_dashes_regex, '', $sub_items[0] );

			// ...and use as the key here, while the sub items go though another
			// round of splitting
			$return[$sub_key] = string_to_array( $sub_items[1], $level );

		// If not, there are no more levels here, so clean and add the value
		else :
			$value = preg_replace( $clean_dashes_regex, '', $value );

			$return[$value] = $value;
		endif;
	endforeach;

	return $return;
}