Expanding sizes between given values

This a very simple function to expand the sizes between the given values.

For instance, if the input variable is "S-XL" then the function returns "S, M, L, XL".

Basically I'm not happy with this function. I think it's too complex for its purpose.

function sizexpander($sizes) {
    $sizearray=Array("XS", "S", "M", "L", "XL", "XXL", "XXXL");
    $size1=array_search(strstrb($sizes, "-"), $sizearray);
    $size2=array_search(substr(strstr($sizes, "-"),1), $sizearray);
    while ($size1 <= $size2) {
        $prodsizes.= $sizearray[$size1].", ";
        $size1++;
    }
    return substr($prodsizes, 0, -2);
}

function strstrb($h,$n){
    return array_shift(explode($n,$h,2));
}

You can use the function array_slice to take the subarray which contains the sizes from $size1 to size2. And then use implode to turn this subarray into a comma-separated string. This will simplify your algorithm.

You can also just use explode instead of substr and strstr to split the range string into its parts.

In addition I would recommend changing the variable names of $size1 and $size2. To me the name $size1 suggests that the variable contains the actual size while in fact it contains its index. Something like index_of_size1 or index_from might be more appropriate.

If I were to write this function, it'd look something like this:

function sizexpander($size_range) {
    $sizearray=Array("XS", "S", "M", "L", "XL", "XXL", "XXXL");
    list($size_from, $size_to) = explode("-", $size_range);
    $index_from = array_search($size_from, $sizearray);
    $index_to = array_search($size_to, $sizearray);
    $subsizes = array_slice($sizearray, $index_from, $index_to-$index_from+1);
    return implode(", ", $subsizes);
}

StackExchange Code Review Q#1043, answer score: 6