Zvýraznění hledaného výrazu v textu s ignorováním velikosti písma a diakritiky; v PHP

excerpt.php

<?php

class Excerpt {
	# transformation rules for characters common in Central Europe
	# at the end there are all [:space:] characters transforrmed to a single space
	private static $transformation = [
		'ä'=>'a',
		'Ä'=>'A',
		'á'=>'a',
		'Á'=>'A',
		'à'=>'a',
		'À'=>'A',
		'ã'=>'a',
		'Ã'=>'A',
		'â'=>'a',
		'Â'=>'A',

		'č'=>'c',
		'Č'=>'C',
		'ć'=>'c',
		'Ć'=>'C',

		'ď'=>'d',
		'Ď'=>'D',

		'ě'=>'e',
		'Ě'=>'E',
		'é'=>'e',
		'É'=>'E',
		'ë'=>'e',
		'Ë'=>'E',
		'è'=>'e',
		'È'=>'E',
		'ê'=>'e',
		'Ê'=>'E',

		'í'=>'i',
		'Í'=>'I',
		'ï'=>'i',
		'Ï'=>'I',
		'ì'=>'i',
		'Ì'=>'I',
		'î'=>'i',
		'Î'=>'I',

		'ľ'=>'l',
		'Ľ'=>'L',
		'ĺ'=>'l',
		'Ĺ'=>'L',

		'ń'=>'n',
		'Ń'=>'N',
		'ň'=>'n',
		'Ň'=>'N',
		'ñ'=>'n',
		'Ñ'=>'N',

		'ó'=>'o',
		'Ó'=>'O',
		'ö'=>'o',
		'Ö'=>'O',
		'ô'=>'o',
		'Ô'=>'O',
		'ò'=>'o',
		'Ò'=>'O',
		'õ'=>'o',
		'Õ'=>'O',
		'ő'=>'o',
		'Ő'=>'O',

		'ř'=>'r',
		'Ř'=>'R',
		'ŕ'=>'r',
		'Ŕ'=>'R',

		'š'=>'s',
		'Š'=>'S',
		'ś'=>'s',
		'Ś'=>'S',

		'ť'=>'t',
		'Ť'=>'T',

		'ú'=>'u',
		'Ú'=>'U',
		'ů'=>'u',
		'Ů'=>'U',
		'ü'=>'u',
		'Ü'=>'U',
		'ù'=>'u',
		'Ù'=>'U',
		'ũ'=>'u',
		'Ũ'=>'U',
		'û'=>'u',
		'Û'=>'U',

		'ý'=>'y',
		'Ý'=>'Y',

		'ž'=>'z',
		'Ž'=>'Z',
		'ź'=>'z',
		'Ź'=>'Z',

		"\x9"=>' ',
		"\xa"=>' ',
		"\xb"=>' ',
		"\xc"=>' ',
		"\xd"=>' '
	];

	# original text
	private $text;
	# text without diacritic marks
	private $textAscii;
	# length of the text in characters
	private $textLength;
	# array of [start and end] positions of runs of spaces
	private $textSpaces;

	# original search
	private $search;
	# search without diacritic marks
	private $searchAscii;
	# length of the search in characters
	private $searchLength;
	# array of positions of searchAscii inside textAscii (ignoring cases)
	private $searchPositions;

	public function __construct($text, $search) {
		$this->text = $text;
		$this->textAscii = self::toAscii($text);
		$this->textLength = mb_strlen($text);
		$this->findSpaces();

		$this->search = $search;
		$this->searchAscii = self::toAscii($search);
		$this->searchLength = mb_strlen($search);
		$this->findPositions();
	}

	# removes diacritic marks from text and replaces all blanks with a single space
	private static function toAscii($str) {
		return strtr($str, self::$transformation);
	}

	# sets positions of searchAscii inside textAscii
	private function findPositions() {
		$this->searchPositions = [];
		$pos = 0;
		while (($pos = mb_stripos($this->textAscii, $this->searchAscii, $pos)) !== FALSE) {
			$this->searchPositions[] = $pos;
			$pos += $this->searchLength;
		}
	}

	# sets start and end positions of runs of spaces in textAscii
	# it makes sure that the beginning and the end of the textAscii are considered a space
	private function findSpaces() {
		# find all spaces
		$spaces = [];
		$pos = 0;
		while (($pos = mb_strpos($this->textAscii, ' ', $pos)) !== FALSE) {
			$spaces[] = $pos;	
			$pos++;
		}

		# now we shall merge runs of spaces into a single record
		# and deal with the beginning and the end

		$this->textSpaces = [];
		if (count($spaces) == 0 || $spaces[0] > 0) {
			# add beginning
			$this->textSpaces[] = [0, 0];
		}

		for ($i = 0; $i < count($spaces);) {
			# process middle
			$s = $i;
			for ($i++; $i < count($spaces) && $spaces[$i] - $spaces[$s] == $i - $s; $i++);
			$this->textSpaces[] = [$spaces[$s], $spaces[$i - 1] + 1];
		}

		if (count($spaces) == 0 ? $this->textLength > 0 : $spaces[count($spaces) - 1] < $this->textLength - 1) {
			# add end
			$this->textSpaces[] = [$this->textLength, $this->textLength];
		}
	}

	# find the best region for the excerpt depending on where the search positions are
	# and depending on the length of the excerpt
	private function findBestPart($length) {
		if (count($this->searchPositions) == 0) {
			# couldn't find $search anywhere
			# let's assume part of the text from the beginning
			return [0, 0];
		}

		# let's find longest subsequence (of limited length) which contains most occurences
		$bestFrom = 0;
		$bestTo = -1;

		$from = 0; # $from is tail, $to is head
		for ($to = 0; $to < count($this->searchPositions); $to++) {
			# moving the tail to keep the body <= $length
			while ($this->searchPositions[$to] - $this->searchPositions[$from] + $this->searchLength > $length) {
				$from++;
			}

			# does the body contain more occurences?
			if ($to - $from > $bestTo - $bestFrom) {
				$bestFrom = $from;
				$bestTo = $to;
			}
		}

		return [
			$this->searchPositions[$bestFrom],
			$this->searchPositions[$bestTo] + $this->searchLength
		];
	}

	# alternate extending the region left and right until it exceed the $length or run out of text
	private function extendExcerpt($start, $end, $length) {
		# first we find the surrounding spaces for the given region

		$startIndex = 0;
		$endIndex = NULL;

		foreach ($this->textSpaces as $index => $space) {
			if ($space[1] <= $start) {
				$startIndex = $index;
			}
			if ($endIndex == NULL && $space[0] >= $end) {
				$endIndex = $index;
			}
		}

		# now we know which space is before and which is after
		# let's extend the text until it excides $length

		$changes = 1;
		# until the region exceeds $length or it stops changing
		while ($this->textSpaces[$endIndex][0] - $this->textSpaces[$startIndex][1] < $length && $changes > 0) {
			$changes = 0;

			if ($startIndex > 0) {
				$startIndex--;
				$changes++;
			}

			if ($endIndex < count($this->textSpaces) - 1) {
				$endIndex++;
				$changes++;
			}
		}

		# now we have the correct limits, which can be slightly bigger than $length

		return [$this->textSpaces[$startIndex][1], $this->textSpaces[$endIndex][0]];
	}

	# finds the region or full words which contains most occurences of search
	# or the beginning of the text if none were found
	# the excerpt is limited by the $length, which it is allowed to exceed.
	private function findExcerpt($length) {
		list($start, $end) = $this->findBestPart($length);
		return $this->extendExcerpt($start, $end, $length);
	}

	public function extract($length = 150, $wrapFunc = NULL) {
		list($start, $end) = $this->findExcerpt($length);

		$excerpt = mb_substr($this->text, $start, $end - $start);

		# if no wrapFunc was given, just return the excerpt
		if (!is_callable($wrapFunc)) {
			return $excerpt;
		}

		# otherwise split the excerpt into parts
		# the wrapFunc is applied to each occurence of the search
		# the rest is kept unchanged

		$parts = [];
		$position = $start;
		foreach ($this->searchPositions as $searchPosition) {
			if ($searchPosition >= $position && $searchPosition + $this->searchLength <= $end) {
				if ($searchPosition > $position) {
					# part between searches or at the beginning of the excerpt
					$parts[] = mb_substr($excerpt, $position - $start, $searchPosition - $position);
				}

				# occurence of the search
				$search = mb_substr($excerpt, $searchPosition - $start, $this->searchLength);
				$parts[] = call_user_func($wrapFunc, $search);

				$position = $searchPosition + $this->searchLength;
			}
		}

		if ($position < $end) {
			# part at the end of the excerpt
			$parts[] = mb_substr($excerpt, $position - $start, $end - $position);
		}

		# all parts are glued together
		return implode("", $parts);
	}
}