When trying to use my search engine using this code

function boolean_sql_select_short($string,$match){
	$match_a = explode(',',$match);
	$score_unit_weight = .2;
	for($ith=0;$ith<count($match_a);$ith++){
		$score_a[$ith] =
			"$score_unit_weight*(
			LENGTH($match_a[$ith]) -
			LENGTH(REPLACE(LOWER('$match_a[$ith]'),LOWER('$string'),'')))/LENGTH('$string')";
	}

               $score = implode(" + ",$score_a);

	return $score;
}

I get the following retuned error:

Warning: implode() [function.implode]: Bad arguments. in /*/*/public_html/search/mysql_boolean.txt on line 45
You have an error in your SQL syntax. Check the manual that corresponds to your MySQL server version for the right syntax to use near ') - LENGTH(REPLACE(LOWER(''),LOWER('eyb'),'')))/LENGTH('eyb'

Need help solving this issue, thanks.