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PHP

Posted by Marty Hitchcock
Marty Hitchcock
13,108 Points

undefined variable

I have just started working on my first PHP project and need a little help. I am trying to make a calendar but have been stuck on a certain aspect for awhile. Can someone please look at my code and explain why I am getting the errors that I am?

$day = date("d");
$month = date("m");
$year = date("y");
// Get the days of the month
$days_in_month = cal_days_in_month(CAL_GREGORIAN,$month,$year);

// Print each day
function print_days($days_in_month) {
    $x = 0;
        while ($days_in_month > $x){
            $x += 1;
            $date = '<div class="box">' . $x . '</div>';
        }
        return $date;
}

Error messages I am getting are as follows. Another thing to note is that I have echoed out all of the variables before the function and they are set correct.

Notice: Undefined variable: days_in_month in on line 13

function print_days($days_in_month) {

Notice: Undefined variable: days_in_month in on line 15

while ($days_in_month > $x){

Notice: Undefined variable: date in on line 19

return $date;

Any help would be appreciated. Not only would I love to get past this wall but understanding why would be a great thing to learn.

2 Answers

Ron McCranie
Ron McCranie
7,837 Points

Here's what I did and it worked. Sorry it took so long, upgraded to OSX Yosemite recently and hadn't reconfigured this computer for development.

// Your variables were outside the function (outside of scope) so the function couldn't access them unless you passed them into the function.
function print_days() { // removed requiring the $days_in_month as we placed it inside the scope of the function
    $day = date("d");
    $month = date("m");
    $year = date("Y"); // 4 digit year using the upper case 'Y'
    // Get the days of the month
    $days_in_month = cal_days_in_month(CAL_GREGORIAN,$month,$year);

    $html = '';  // here's our html output, we will start empty and let the while loop populate it a piece at a time

    while ($days_in_month > $x){
        $html .= "<div class='box'>".$x."</div>\n"; // used '.=' so it appends this html to what was already in the $html variable, otherwise you will overwrite it every time you go through the loop. placed the '/n' at the end to make a new line in the html (easier to read), placed the html in double quotes to that the /n would work.
        $x++; // '++' means go up by 1
    }

    echo $html; // don't need to return anything if you want it to print the divs, just echo it here

}

print_days();

If you need any explanation please let me know.

Marty Hitchcock
Marty Hitchcock
13,108 Points

I thought that including the variable inside the parenthesis of the function like I did made them available for the function, is that not the case?

Thanks so much for all of your help. Have taught me a bunch!

Ron McCranie
Ron McCranie
7,837 Points
Ron McCranie
Ron McCranie
7,837 Points

Looks like a problem with you defining $days_in_month check the syntax on the cal_days_in_month() http://www.php.net/manual/en/function.cal-days-in-month.php

if the syntax is correct, then maybe a value you're passing to it is off. I think it requires a 4 digit year and you might be passing a 2 digit year. date('y') = 2 digits, date('Y') = four digits. http://www.php.net/manual/en/function.date.php

I would do a for loop instead of the while. If you stick with the while then I would make the incrementing $x++; and place it as the last line of the while (convention).

Marty Hitchcock
Marty Hitchcock
13,108 Points

Thanks for the help. But as I said, I echoed out all of the variables before the function and they were all correct (the $days_in_month was set to 31).

As for the loop, I will do some reading and try familiarize myself with the differences better and what the ++ does.