Replaces end quotes with the appropriate accent (Italian)

addAccentMarksForItalian.php

<?php
  
/**
 * The MIT License (MIT)
 * 
 * Copyright (c) 2016 Francis Laclé
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *   
 * The above copyright notice and this permission notice shall be included in 
 * all copies or substantial portions of the Software.
 *   
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

/**
 * Replaces end quotes with the appropiate accent mark for Italian
 * @param $str a string containing text.
 * Author: Francis Laclé
 */
function replaceEndQuote(&$str) {
	$out = '';
	$words = explode (' ', $str);
	$vowels = 'aioue'; // 'e' is last as this is handled separately
	$acuteVowels = 'àìòù';

	/**
	 * Diacritical rules taken from :
	 * http://italian.about.com/od/pronunciation/fl/italian-accent-marks.htm
	 * Limitations:
	 * - does not take da' (imperative of dare) into account
	 * - does not take di' (imperative form of dire) into account
   */

	foreach($words as $word) {

  	// How long is the word?
		$len = strlen($word);

		// Does word end with a letter?
		$endIsAlpha = preg_match('/[a-zA-Z]/i', substr($word, $len-1, $len));
		
		// Track number of uppercases to apply back later
		$upperCaseIndices = '';
		for($l = 0; $l < $len; $l++) {
  		$letter = substr($word, $l, 1);
      if(strtolower($letter) !== $letter) {
        $upperCaseIndices.= '1'; 
      } else {
        $upperCaseIndices.= '0'; 
      }
		}
		
		// Convert the word to lower case for further comparison
		$word = strtolower($word);

		// We assume a mismatch
		$match = false;

		// Storage for non-alpha character such as comma's, exclamation, dots, etc.
		$lastChar = '';

		// Check if word starts with a single quote as well (we discard those)
		if(strpos($word, '\'') === 0) {
  		$match = true; // this is so we can skip everything else
		}

		// Check if word does not end with a letter
		if(!$endIsAlpha && !$match) {
  		$lastChar = substr($word, $len-1, $len);
  		// If it is not a single quote we keep the copy and remove the char
  		if(strpos($lastChar, '\'') !== 0) {
    	  $word = substr($word, 0, $len-1);
    	  $len = strlen($word);
  		} else {
    		// We don't store the char as single-quotes have to be replaced
    		$lastChar = '';
  		}
		}

		// Check the special case for e' as a verb
		if($len === 2 && $word === 'e\'' && !$match) {
  		$word = 'è';
  		$match = true;
		}

		// Check the special case of tea and not coffee :p
		if($len === 3 && $word === 'te\'' && !$match) {
  		$word = 'tè';
  		$match = true;
		}

		// Check the special case of de'
		if($len === 3 && $word === 'de\'' && !$match ) {
  		$match = true;
		}

		// Continue if mismatch is still valid
		if(!$match) {

  		// Only process words that end with a single quote
  		if(strrpos($word, '\'') === $len-1) {
        // This is to check if the last & second-last letters end with a vowel
    		$lastLetter = substr($word, $len-2, 1);
    		$secondLastLetter = substr($word, $len-3, 1);

        // Check for 'e' again as it has more rules and exceptions
        if($lastLetter === 'e') {
          // Does 'e' come after a vowel?
          if(strpos($vowels, $secondLastLetter) !== false) {
            // We add a grave accent
            $word = str_replace('e\'', 'è', $word);
          } else {
            // We add an acute accent
            $word = str_replace('e\'', 'é', $word);
          }
          $match = true;
        }

        // Check for other vowels
        if(strpos($vowels, $lastLetter) !== false && !$match) {
          for($v = 0; $v < strlen($acuteVowels); $v++) {
            if(substr($vowels, $v, 1) === $lastLetter) {
              // Replace the vowel with corresponding acute accented letter
              $word = str_replace(
                $lastLetter.'\'',
                mb_substr($acuteVowels, $v, 1),
                $word
              );
              $match = true;
              break;
            }
          }
        }
  		}
		}
		
		// Convert back to uppercase if necessary
		$casedWord = '';
		for($l = 0; $l < $len; $l++) {
  		$letter = mb_substr($word, $l, 1);
      $upperCaseIndex = substr($upperCaseIndices, $l, 1);
      if($upperCaseIndex === '1') {
        $casedWord.= mb_strtoupper($letter);
      } else {
        $casedWord.= $letter;
      }
		}
		
		$word = $casedWord;
    $out.= ' '.$word.$lastChar;

	}

	return $out;
}

// Example below tests both lower and upper case and some exceptions/edge-cases.
header('Content-type: text/plain; charset=utf-8');
$str = "Questa CitTA' citta' di nome 'ROMA' E' e' davvero bella ".
       "poiche' Poiche' molto te' TE', antica piu' PIU'.";
echo 'Input: '.$str.PHP_EOL.'- - - - - -'.PHP_EOL;
echo 'Result: '.replaceEndQuote($str);

?>