Switch Case - not all cases work

Question

At the moment I am writing a calendar. According to the chosen motn ($monthnum), I store the abbreviated month name ($monthabbr) in a database. For that I use a switch-case construct. It works for all months, except for 08-August and 09-September. Since I used the same code for all months, I don't know why it's not working. I am close to the edge to start all over again, but before that I'll better ask if you see an error.

switch( $monthnum ) {
            case 01:
                $monthabbr = 'Jan';
                break;
            case 02:
                $monthabbr = 'Feb';
                break;
            case 03:
                $monthabbr = 'Mär';
                break;
            case 04:
                $monthabbr = 'Apr';
                break;
            case 05:
                $monthabbr = 'Mai';
                break;
            case 06:
                $monthabbr = 'Jun';
                break;
            case 07:
                $monthabbr = 'Jul';
                break;
            case 08:
                $monthabbr = 'Aug';
                break;
            case 09:
                $monthabbr = 'Sep';
                break;
            case 10:
                $monthabbr = 'Okt';
                break;
            case 11:
                $monthabbr = 'Nov';
                break;
            case 12:
                $monthabbr = 'Dez';
                break;
}

Answer 1

Change 01, 02, ..., 09 to just 1, 2, ..., 9 (drop the zeros).

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By starting an integer literal with a 0 indicates that it should be interpreted as an octal number (a number in base 8).

For octal numbers the digits 8 and 9 are illegal.

Further reading:

• PHP Manual: Integers

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(Btw, you may want to consider using an array or a map from integer to string, and just look up the string using something like monthAbbrs[$monthnum])