Question

Struggling with this tournament fixtures algorithm.

The code is working perfectly but I need help inserting the data to mysql
I cant seem to access the $varables..

any tweaking by a php pro greatly appreciated …

$teamnames = "Arsenal|Tottenham|Leeds|Man United|Liverpool";



        # XXX check for int
        print show_fixtures(isset($_GET['teams']) ?  nums(intval($_GET['teams'])) : explode("|", trim($teamnames)));


function nums($n) {
    $ns = array();
    for ($i = 1; $i <= $n; $i++) {
        $ns[] = $i;
    }
    return $ns;
}

function show_fixtures($names) { 
    $teams = sizeof($names);

    print "<p>Fixtures for $teams teams.</p>";

    // If odd number of teams add a "ghost".
    $ghost = false;
    if ($teams % 2 == 1) {
        $teams++;
        $ghost = true;
    }

    // Generate the fixtures using the cyclic algorithm.
    $totalRounds = $teams - 1;
    $matchesPerRound = $teams / 2;
    $rounds = array();
    for ($i = 0; $i < $totalRounds; $i++) {
        $rounds[$i] = array();
    }

    for ($round = 0; $round < $totalRounds; $round++) {
        for ($match = 0; $match < $matchesPerRound; $match++) {
            $home = ($round + $match) % ($teams - 1);
            $away = ($teams - 1 - $match + $round) % ($teams - 1);
            // Last team stays in the same place while the others
            // rotate around it.
            if ($match == 0) {
                $away = $teams - 1;
            }
            $rounds[$round][$match] = team_name($home + 1, $names) 
                . " v " . team_name($away + 1, $names);


        }
    }

    // Interleave so that home and away games are fairly evenly dispersed.
    $interleaved = array();
    for ($i = 0; $i < $totalRounds; $i++) {
        $interleaved[$i] = array();
    }

    $evn = 0;
    $odd = ($teams / 2);
    for ($i = 0; $i < sizeof($rounds); $i++) {
        if ($i % 2 == 0) {
            $interleaved[$i] = $rounds[$evn++];
        } else {
            $interleaved[$i] = $rounds[$odd++];
        }
    }

    $rounds = $interleaved;

    // Last team can't be away for every game so flip them
    // to home on odd rounds.
    for ($round = 0; $round < sizeof($rounds); $round++) {
        if ($round % 2 == 1) {
            $rounds[$round][0] = flip($rounds[$round][0]);
        }
    }

    // Display the fixtures        
    for ($i = 0; $i < sizeof($rounds); $i++) {
        print "<hr><p>Round " . ($i + 1) . "</p>\n";
        foreach ($rounds[$i] as $r) {


      print $r . "<br />"; 


        }
        print "<br />";
    }
    print "<hr>Second half is mirror of first half";
    $round_counter = sizeof($rounds) + 1;
    for ($i = sizeof($rounds) - 1; $i >= 0; $i--) {
        print "<hr><p>Round " . $round_counter . "</p>\n";
        $round_counter += 1;
        foreach ($rounds[$i] as $r) {
            print flip($r) . "<br />";
        }
        print "<br />";
    }
    print "<br />";

    if ($ghost) {
        print "Matches against team " . $teams . " are byes.";
    }
}

function flip($match) {
    $components = split(' v ', $match);


    return "$components[1]" . " v " . "$components[0]";

}

function team_name($num, $names) {
    $i = $num - 1;
    if (sizeof($names) > $i && strlen(trim($names[$i])) > 0) {
        return trim($names[$i]);
    } else {
        return "BYE";
    }
}

Answer 1

I’m not entirely sure what you’re hung up on (you should really be more specific in your questions, as specified by the FAQ), but I suspect it is a matter of scope.

When you set a variable within a function, that variable is only accessible within that function. For example:

function do_something() {
    $a = 'something!';
}
do_something();
echo $a;

This should result in PHP notice telling you that PHP doesn’t know what $a is in the scope that it is trying to echo. Now, if I modify this script…

$a = '';
function do_something() {
    global $a; // Lets PHP know we want to use $a from the global scope
    $a = 'something!';
}
do_something();
echo $a;

This will work and output “something!”, because $a is being “defined” in the scope outside of the function.

You can read more about variable scope in the PHP documentation: http://php.net/manual/en/language.variables.scope.php

Now, something else you need to pay attention to is outputting user data. In your script, you take data straight from $_GET and print it out to the page. Why is this bad? Someone could inject some nice JavaScript into your page (or anything they wanted) and steal users’ sessions. You should be using htmlspecialchars() any time you need to output a variable. Even if it is just a team name, you never know when some team will stick a ; or < or > or some other reserved character in there.

Finally, I strongly recommend not mixing your logic with your computation. Let your program figure everything out, and then loop through the data for your output. You should be able to save the entire data for this type of problem in a nice associative array, or some crafty object you come up with.