LEVENSHTEIN(3)								 1							    LEVENSHTEIN(3)

levenshtein - Calculate Levenshtein distance between two strings

SYNOPSIS

       int levenshtein (string	$str1, string  $str2)

DESCRIPTION

       int levenshtein (string	$str1, string  $str2, int  $cost_ins, int  $cost_rep, int  $cost_del)

	The  Levenshtein  distance  is	defined  as the minimal number of characters you have to replace, insert or delete to transform $str1 into
       $str2. The complexity of the algorithm is O(m*n), where n and m are the length of $str1 and $str2  (rather  good  when  compared  to  simi-
       lar_text(3), which is O(max(n,m)**3), but still expensive).

	In  its  simplest  form the function will take only the two strings as parameter and will calculate just the number of insert, replace and
       delete operations needed to transform $str1 into $str2.

	A second variant will take three additional parameters that define the cost of insert, replace and delete operations. This is more general
       and adaptive than variant one, but not as efficient.

PARAMETERS

	      o $str1
		- One of the strings being evaluated for Levenshtein distance.

	      o $str2
		- One of the strings being evaluated for Levenshtein distance.

	      o $cost_ins
		- Defines the cost of insertion.

	      o $cost_rep
		- Defines the cost of replacement.

	      o $cost_del
		- Defines the cost of deletion.

RETURN VALUES

	This  function	returns the Levenshtein-Distance between the two argument strings or -1, if one of the argument strings is longer than the
       limit of 255 characters.

EXAMPLES

       Example #1

	      levenshtein(3) example

	      <?php
	      // input misspelled word
	      $input = 'carrrot';

	      // array of words to check against
	      $words  = array('apple','pineapple','banana','orange',
			      'radish','carrot','pea','bean','potato');

	      // no shortest distance found, yet
	      $shortest = -1;

	      // loop through words to find the closest
	      foreach ($words as $word) {

		  // calculate the distance between the input word,
		  // and the current word
		  $lev = levenshtein($input, $word);

		  // check for an exact match
		  if ($lev == 0) {

		      // closest word is this one (exact match)
		      $closest = $word;
		      $shortest = 0;

		      // break out of the loop; we've found an exact match
		      break;
		  }

		  // if this distance is less than the next found shortest
		  // distance, OR if a next shortest word has not yet been found
		  if ($lev <= $shortest || $shortest < 0) {
		      // set the closest match, and shortest distance
		      $closest	= $word;
		      $shortest = $lev;
		  }
	      }

	      echo "Input word: $input
";
	      if ($shortest == 0) {
		  echo "Exact match found: $closest
";
	      } else {
		  echo "Did you mean: $closest?
";
	      }

	      ?>

	      The above example will output:

	      Input word: carrrot
	      Did you mean: carrot?

SEE ALSO

       soundex(3), similar_text(3), metaphone(3).

PHP Documentation Group 													    LEVENSHTEIN(3)