some Simple Implementation of isBalanced function

blancedBracket.php

<?php

function isBalanced($string)
{
    $str = preg_replace('([^\(\)])', '', $string);

    if($str == ""){
        return TRUE;
    }

    $strArray = str_split($str);

    $ImbalanceCounter = 0;

    foreach($strArray as $bracket){
        $ImbalanceCounter = $bracket == '(' ? $ImbalanceCounter + 1 : $ImbalanceCounter - 1;

        if($ImbalanceCounter < 0){
            return false;
        }
    }

    return ($ImbalanceCounter == 0);
}


function isBalanced2($string)
{
    $cleanStr = preg_replace('([^\(\)])', '', $string);

    if($cleanStr == ""){
        return TRUE;
    }
    if(!function_exists('iterate')){
        function iterate($str, $count = 0){
            if(empty($str)){
                return $count == 0;
            }else{
                $count = substr($str, 0,1) == '(' ? $count + 1 : $count - 1;
                return ($count >= 0) ? iterate(substr($str, 1,strlen($str)-1), $count): FALSE;
            }
        }
    }

    return iterate($cleanStr);
}

function isBalanced3($str, $count = 0)
{
    if (empty($str)) {
        return $count == 0;
    }

    switch ($str[0]) {
        case "(" :
            $count++;
            break;
        case ")" :
            $count--;
            break;
    }
    return ($count >= 0) ? isBalanced3(substr($str, 1), $count) : FALSE;
}

//Shorter Implementation of Imran vai's Method
function isBalanced4($string){
     $str = preg_replace('([^\(\)])', '', $string);
 	 do{
	   $str = str_replace("()", "", $str, $count);
	 }while($count>0 && $str!="");
	return $str == ""; 
}


echo "String 1 test: ";
var_dump(isBalanced("balance: '(if (zero? x) max (/ 1 x))' is balanced"));
echo "String 2 test: ";
var_dump(isBalanced2("I told him (that it's not (yet) done)(.\n(But he wasn't listening)"));
echo "String 3 test: ";
var_dump(isBalanced3("())()"));