Date comparisons

[SPetty]

I am trying to make a date comparison so that if the submitted date (submitted in fields of start_date_day, start_date_month, start_date_year and the corresponding end_date_xxxx) is greater or equal to the current date (format d/m/yyyy no zeros) then the block of code will run. If not, nothing gets displayed.

In trying to make my comparisons using this code:

			
if ($row['end_date_year'] = "")
{
   if ($row['start_date_year'] >= date("Y") and $row['start_date_month'] >= date("n"))
   {
        if ($row['start_date_day'] >= date("j"))
       {			
						include 'data/listing_code.php';
       }
   }
}
else
{
   if ($row['end_date_year'] >= date("Y") and $row['end_date_month'] >= date("n") and $row['end_date_day'] >= date("j"))
   {
	include 'data/listing_code.php';
   }
}

I keep running into instances where what should be a valid date, ends up being kicked out because it isn't satisfying the function. I am lost on where I should begin in order to make a date comparison that will truly verify the submitted date is current, or upcoming.

Thanks!
Shawn

[visualAd]

Firstly, you are using the assignment operator when you should be using the comparison operator "==":

/* allways evaluates to false as it is assigning the null stirng to $row['end_date_year'] */
if ($row['end_date_year'] = "") 

/* it should be */
if ($row['end_date_year'] == "") 

Secondly, when making multiple comparisons in a single if statement, you should enclose each distinct test in the expression in brackets:

if (($row['start_date_year'] >= date("Y")) && ($row['start_date_month'] >= date("n"))) 

Also, notice how && is use instead of and. && increases the efficiency of the code, as if one of the test fail, it immediatly stops evaluating any of the other tests in that expression.

Now to the problem. All these data are intergers, correct? So, why not use the mktime() function, it is a lot easier to then compare the dates:

// returns an integer timestamp for current day
$curday = mktime(0,0,0, date('n'), date('d'), date('Y'));

if ($row['end_date_year'] == "")
{
   $start_time = mktime(0,0,0, $row['start_date_month'], $row['start_date_day'],  $row['start_date_year']);


if ($start_time >= $curday)
{    
     include 'data/listing_code.php';
}
}
else
{
   $end_time = mktime(0,0,0, $row['end_date_month'], $row['end_date_day'],  $row['end_date_year']);

   if ($end_time >= $curday)
   {
       include 'data/listing_code.php';
   }
} 

[Frederick]

visualAd wrote:

why not use the mktime() function, it is a lot easier to then compare the dates

To add to the above, when adding a date to your database field, use time() instead of a string date. This way you do not have to do any convertions for checking and matching.

SQL insert item:
$postdate = time();

Use as follows:

$checkdate = ($time() - 3600);
if ($row['fieldname'] <= $checkdate) {
    echo "Go";
} else {
    echo "NoGo";
}

[SPetty]

Thanks VisualAd for the code correction as well as the mktime() usage. Works like a charm now!

I am also using timestamps when an event is added into my database, as I will be using it to send email updates to my visitors.

Thanks again!
Shawn

[Weedpacket]

If you are going to use a string-formatted date, use a date type for the database field, and format the string in ISO8601 form "yyyy-mm-dd". (There are solid reasons for preferring this format - it's not just something ISO picked out at random.) Any sensible DBMS will recognise the form and store it correctly.

[Roger_Ramjet]

Weedpacket wrote:

If you are going to use a string-formatted date, use a date type for the database field, and format the string in ISO8601 form "yyyy-mm-dd". (There are solid reasons for preferring this format - it's not just something ISO picked out at random.) Any sensible DBMS will recognise the form and store it correctly.

And it allows you to use the mysql date functions in your queries to both perform calculations on the data and to format it for output.

[visualAd]

The MySql date format also has support for dates prior to Fri, 13 Dec 1901 and provides a function to convert it to a unix timestamp.for use in PHP.