<?php
/**
 * This class compares two strings and outputs the similarities  as percentage
 *
 *@author Rochak Chauhan <hide@address.com>
 */
class PhpCompareStrings{
	private $str1="";
	private $str2="";
	
	private $arr1=array();
	private $arr2=array();	
	
	/**
	 *Contructor fucntion
	 *
	 *@param string $str1
	 *@param string $str2
	 *@return string
	 */
	function __construct($str1,$str2){
		$str1=trim($str1);
		$str2=trim($str2);
		if($str1==""){ trigger_error("First parameter can not be left blank", E_USER_ERROR); }
		elseif($str2==""){ trigger_error("Second parameter can not be left blank", E_USER_ERROR); }
		else{
			$this->str1=$str1;
			$this->str2=$str2;
			$this->arr1=explode(" ",$str1);
			$this->arr2=explode(" ",$str2);
		}
	}
	
	/**
	 *Function to compare two strings and return the similarity in percentage
	 *
	 *@access public
	 *@return float
	 */
	public function getSimilarityPercentage(){
		$str1=$this->str1;
		$str2=$this->str2;		
		$tmp1=$this->arr1;
		$c1=count($tmp1);
		$tmp2=$this->arr2;		
		$c2=count($tmp2);		
		$count=$c1;
		$t1=$tmp1;
		$t2=$tmp2;
		if($c2>$c1){			
			$count=$c2;
			$t1=$tmp1;
			$t2=$tmp2;
		}		
		$result=array();
		for($i=0;$i<$count;$i++){			
			if(@$t1[$i]==@$t2[$i]){
				$result[]=1;
				$resultSame[]=0;
			}
			else{
				$result[]=0;
				$resultSame[]=levenshtein(@$t1[$i],@$t2[$i]);
			}		
		}
		$countArray=array_count_values($result);					
		$one=0;
		$zero=0;
		if(isset($countArray[0])){ $zero=$countArray[0]; }
		if(isset($countArray[1])){ $one=$countArray[1]; }		
		if($one===0){ $percent=number_format(0,2); }
		elseif($zero===0){ $percent=number_format(100,2); }
		else{ 
			$per=($one/($one+$zero))*100;
			$percent=number_format($per,2);
		}
		if($c1===$c2){
			$words1 = array_diff_assoc($tmp1,$tmp2);
			$words2 = array_diff_assoc($tmp2,$tmp1);
			$sum=array_sum($resultSame);
			$sum=($sum/100);
			$percent=($percent-$sum);
		}
		return $percent;
	}
	
	/**
	 *Function to compare two strings and return the difference in percentage
	 *
	 *@access public
	 *@return float
	 */
	public function getDifferencePercentage(){
		$per=$this->getSimilarityPercentage();
		return 100-$per;
	}
}
?>