如何实现php字符串转换成数组

<?php
$str = 'con[1]=28&selt[1]=1&con[2]=29&selt[2]=4&con[3]=26&selt[3]=4&con[4]=30&selt[4]=2&con[5]=4&selt[5]=1&con[6]=11&con[7]=12';
$arr = explode('&',$str);
$arr2 = array();
foreach($arr as $k=>$v){
        $arr = explode('=',$v);
        $arr2[$k] = $arr[1];
}
print_r($arr2);
?>
//输出
Array
(
    [0] => 28
    [1] => 1
    [2] => 29
    [3] => 4
    [4] => 26
    [5] => 4
    [6] => 30
    [7] => 2
    [8] => 4
    [9] => 1
    [10] => 11
    [11] => 12
)
//第二个
<?php
$str = 'con[1]=28&selt[1]=1&con[2]=29&selt[2]=4&con[3]=26&selt[3]=4&con[4]=30&selt[4]=2&con[5]=4&selt[5]=1&con[6]=11&con[7]=12';
$arr = explode('&',$str);
$arr2 = array();
foreach($arr as $k=>$v){
        $arr = explode('=',$v);
        $arr2[$arr[0]] = $arr[1];
}
print_r($arr2);
?>
//输出
Array
(
    [con[1]] => 28
    [selt[1]] => 1
    [con[2]] => 29
    [selt[2]] => 4
    [con[3]] => 26
    [selt[3]] => 4
    [con[4]] => 30
    [selt[4]] => 2
    [con[5]] => 4
    [selt[5]] => 1
    [con[6]] => 11
    [con[7]] => 12
)

parse_str(string,array)
string:需要转换的字符串；
array:返回到一个数组中；
如果没有设置array的话就覆盖同名变量