PHP while loop for HTML Generation: Should I Check Array values at each While Loop Iteration or use Post-Loop String Processing?

Question

I'm working on a PHP-written html calendar that writes each day of the month inside a while loop.

Each day of the month is inside a pair of tags and certain days need a title attribute in the tag. Those days will be obtained from the MySQL db and stored in an array like this: $array($day_number=>$quantity).

An example array might be: (3=>5, 12=>4, 15=>6, 22=>10, 27=>2, 31=>4). The array would only contain keys for days where the quantity is not zero.

I can think of two ways to do this. I'm wondering which one is more efficient, or if there is another, best way.

Option 1.) Check the array at each iteration of the html-creating loop to see if it contains the corresponding day. If so, add the appropriate title attribute to the tag. So I would be using something like:

$day = 1;
while($day < 31) {
if(array_key_exists($day,$array)) {
echo "<td title=\"$array['$day'] spots available\">$day</td>";
}
else echo "<td title\"No spots available for this date\">$day</td>";
$day++;
}

2.) Use loop to put entire calendar into a string variable, then use string functions to insert special title attributes.

$day = 1;
while($day < 31) {
$month .= "<td>$day</td>";
$day++;
}
foreach($array as $day_number=>$quantity) {
$month = str_replace("<td>$day_number</td>","<td title=\"$quantity spots available\">$day_number</td>",$month)
}

In this application, either method will be done very quickly but my question is more general. Is it better to use string functions after the loop that creates the basic html, or to checking/processing at each iteration? Or is there a third, best way?

I have learned PHP entirely by myself using internet resources so I have no idea how bad my coding may be. Any help is appreciated.

Thank you.

Halcyon · Accepted Answer · 2011-06-20 20:02:56Z

1

Here's another solution:

$day = 1;
$strings = array();
while($day < 31) {
    if (array_key_exists($day, $array)) {
        $strings[$day] = $array['$day'] . " spots available";
    } else {
        $strings[$day] = "No spots available for this date";
    }
    $day += 1;
}
foreach ($strings as $day => $string) {
    echo '<td title="' . $string . '">' . $day . '</td>';
}

What is so different about it? Well, fist of all, it's likely going to be slower than your solution since I'm looping 31 times, twice! But this example is so trivial that performance is not your main concern. Your main concern is writing code that is so simple anyone can understand it.

PHP code gets very complicated if you have lots of HTML printing going on. Generally what you want to do is make some sort of model (adhoc or systematic) that collects all your data, and only prints it to HTML as the very last step.

Learn to separate the data-collection and model generation step from the HTML printing step. This may seem like overkill and a waste of CPU power and memory and what not, but what is more expensive: your time and sanity or some server in a hot room somewhere? ;)

Your choice to have a sparse array of only the days that have spots available is already an optimization. And premature optimization is the mother of all evil. Think about the easiest way to solve your problem, build that, it's likely going to be fast enough anyway.

answered Jun 20, 2011 at 20:02

Halcyon

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1 Comment

Buttle Butkus Over a year ago

Thanks for your answer. I have been thinking too hard about optimization and too little about elegance. I seem to have gotten caught up in some programming authors' weird emphasis on the minutiae of performance. And I still am amazed whenever I write not-100%-efficient code and yet it executes in 5 ms. I like how you separated two processes there, whereas I have been tending to wrack my brain trying to combine as many processes as possible. Thanks for your advice! I will be using it.

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