[RESOLVED] Conditions Based on Dates

Curbuntu

Other than having used some PHP include statements, I'm new to PHP (although I'm working through an O'Reilly book, 'Learning PHP & MySQL').

Is there a PHP way to "include" based on checking the system date? (For ease of use, let's say the server's date.) I envision it working something like this:

If date >= x and date <=y, then "include," otherwise do nothing.

Being able to do this with PHP code would let me pre-load code that would "time in" at a certain date, then "time out" at another date. Right now, I have to do it by hand (for example, see parbarwestward.org/Parbar/NewThisMonth.php

and am unable to insert the code ahead of the time I would like it to appear.

Thanks in advance.

NogDog

$start = strtotime('2008-01-01 00:00:00');
$end = strtotime('2008-02-29 23:59:59');
$now = time();
if($now >= $start and $now <= $end)
{
   include 'some_date_sensitive_file.php';
}

You could use [man]mktime/man instead of [man]strtotime/man if you prefer, but I find the code easier to read this way.

Curbuntu

Now that's what I call a quick reply. Thanks!

Can the same variable names be used on the same page for different dates/includes? IOW, would it work to have

$start = strtotime('2008-01-01 00:00:00');
$end = strtotime('2008-02-29 23:59:59');
$now = time();
if($now >= $start and $now <= $end)
{
include 'some_date_sensitive_file01.php';
}

followed (at some point on the same page) by

$start = strtotime('2008-01-15 00:00:00');
$end = strtotime('2008-03-15:59:59');
$now = time();
if($now >= $start and $now <= $end)
{
include 'some_date_sensitive_file02.php';
}

Or would the start/end variables names have to be altered slightly in each case?

NogDog

You can reuse variables as often as you want. (That's the main reason they are called "variables", as opposed to "constants" whose values cannot be changed.) If desired, you could even avoid using those variables if you wanted to:

$now = time();
if($now >= strtotime('2008-01-01 00:00:00') and $now <= strtotime('2008-02-29 23:59:59'))

Or, if you will have serveral such time intervals and want to store them all in one place (so as to make it easy to change them when needed), you could use a multi-dimension array:

$intervals = array(
   1 => array(
      'start' => strtotime('2008-01-01 00:00:00'),
      'end'   => strtotime('2008-02-29 23:59:59')
   ),
   2 => array(
      'start' => strtotime('2008-03-01 00:00:00'),
      'end'   => strtotime('2008-03-31 23:59:59')
   )
);
$now = time();
if($now >= $intervals[1]['start'] and $now <= $intervals[1]['end'])
{
   // do something
}
if($now >= $intervals[2]['start'] and $now <= $intervals[2]['end'])
{
   // do something else
}

Curbuntu

NogDog wrote:
You can reuse variables as often as you want. (That's the main reason they are called "variables", as opposed to "constants" whose values cannot be changed.)

I figured as much, but wanted to make certain.

NogDog wrote:
If desired, you could even avoid using those variables if you wanted to:
$now = time();
if($now >= strtotime('2008-01-01 00:00:00') and $now <= strtotime('2008-02-29 23:59:59'))

This method has some advantages, one of which is -- fewer lines of code (in a small batch of these statements).

NogDog wrote:
Or, if you will have serveral such time intervals and want to store them all in one place (so as to make it easy to change them when needed), you could use a multi-dimension array:

Now this would be handy on a page requiring a lot of "timed" entries. If the array/variables were declared at the "top" of the page, all of them would be easily accessible, and I wouldn't have to hunt them all down.

NogDog wrote:

$intervals = array(
   1 => array(
      'start' => strtotime('2008-01-01 00:00:00'),
      'end'   => strtotime('2008-02-29 23:59:59')
   ),
   2 => array(
      'start' => strtotime('2008-03-01 00:00:00'),
      'end'   => strtotime('2008-03-31 23:59:59')
   )
);
$now = time();
if($now >= $intervals[1]['start'] and $now <= $intervals[1]['end'])
{
   // do something
}
if($now >= $intervals[2]['start'] and $now <= $intervals[2]['end'])
{
   // do something else
}

And now the light goes on (I think) about what constitutes a "multidimensional array" -- could it also be described as a "nested array"? That is, an "M.d." array is really arrays within an array (and [possibly?] arrays within arrays within an array).

I think that you're managing to "teach me to fish" instead of just giving me a fish sandwich to eat. "Arrays" is the title of the next chapter in my PHP book, and now I can tackle that a little more confidently. Thanks.

NogDog

Yes, a multi-dimension array is an array of arrays [of arrays [etc....]]. Arrays by themselves provide a powerful way to organize data within a script. Additionally, PHP has a large number of array functions which make them even more powerful.

Curbuntu

NogDog wrote:
Yes, a multi-dimension array is an array of arrays [of arrays [etc....]]. Arrays by themselves provide a powerful way to organize data within a script. Additionally, PHP has a large number of array functions which make them even more powerful.

That dim bulb in my head seems to be getting a few watts brighter. So if I think of multidimensional arrays as ad hoc temporary "databases" made up of variables -- and PHP is good at handling these -- then it makes sense why PHP integrates well with mySQL, a symbiotic relationship which allows creation/manipulation/etc. of permanent databases.

If I'm on the right track in this line of thinking, then I'm even happier to be spending time learning this stuff -- it has the potential to pack a lot more power and flexibility into my web designs.

Once again, NogDog, thanks!

Curbuntu

Is it possible to have more than one "if" statement within php brackets

<?php ?>

I have a situation in which I need to list a series of indepenent IF/PRINT conditions. No statement depends on any others, and none requires else or ifelse.

When each statement is isolated within its own set of php brackets, the setup works fine, but trying to incorporate them all within one set of php brackets. I tried putting a ";" after the final "}" of each if statement, but that didn't work.

There doesn't seem to be an endif; statement like the endswitch; statement; at least, it's not shown in my book's examples or in the index.

NogDog

There is, in fact, an alternative syntax for if/else statements that includes an endif; command. However, most coders use the "curly bracket" style. In that case, an IF is terminated by its relevant else {...} if there is one, or else by any command that is not an else or elseif following its closing "}".

<?php
if(condition)
{
   // do something
}
echo "preceding if block is now completed";

if(condition)
{
   // do something
}
elseif(another condtion)
{
   // do something else
}
echo "preceding if/elseif structure is now complete";

if(condition)
{
   // do something
}
elseif(another condtion)
{
   // do something else
}
else
{
   echo "There can only be one else per if/elseif/else structure, so this one will be completed at the closing '}', below.";
}
?>

Curbuntu

Your statement

...an IF is terminated by...any command that is not an else or elseif following its closing "}".

helps me to see why I couldn't make it work.

Okay, so is there an "any command" that is more or less "inert"? IOW, I wouldn't want/need the command to do/print/echo anything; I just need some command to function as a "buffer" between distinct if statements. Maybe I could declare a throw-away variable or something like that?

Your alternative coding page offers an intriguing format:

<?php if ($a == 5): ?>
    A is equal to 5
<?php endif; ?>

Of this structure, it says:

In the above example, the HTML block "A is equal to 5" is nested within an if statement written in the alternative syntax.

This would seem to have some advantages for what I'm doing:

It would appear that any XHTML between "if" and "endif" could be used without slashing quotes (i.e., href=\"whatever.php\"). This would make a clean break between the PHP and XHTML code. And,
Because of the "endif", it wouldn't seem to require some "inert" buffer command between if statements.

Am I correct on both of these points?

It looks like I'll have to keep reminding myself that my "Learning PHP & MySQL" book is strictly introductory, rather than exhaustive or comprehensive.

NogDog

OK, I think I see what you're getting at -- I might have misunderstood the original question. You can exit out of PHP mode within an if block:

<?php
if($x == $y)
{
?>
<p>This text only gets output if the above IF condition evaluates a true.</p>
<?php
} // end of the IF block
?>

Curbuntu

NogDog, this final solution works as smooth as butter. And not having to escape quotes ('\"') in my XHTML allows me to move XHTML code in and out of these specialized if formats without having to remember to "slash" or "unslash."

As for your statement,

I might have misunderstood the original question

I can only say that it's easy to do when you're dealing with someone like me who isn't even certain of the right vocabulary, much less how to articulate the question in an intelligible manner. I learned quite a bit along the way. Thanks!

I don't know how to mark a topic thread like this as "solved," but as far as I'm concerned, it's solved...

NogDog

Just click the "Thread Tools" link at the top of the thread, and you should see a "Mark Thread Resolved" option.