PHP: Which is more efficient: a concatonated return variable, or returning each line individually?

Question

I have a sytem where I want to build an HTML table in PHP from data retrieved from a databse.

I've previously used two different methods for creating the HTML and echoing it.

Building a return variable, and echoing at the end of the PHP script:

<?php
$data['category']['parts']; // format of the data

$retval = '<table>';
foreach($data as $category) {
  $retval .= '<tr>';
  foreach($category as $data) {
    $retval .= '<td>'.$data.'</td>'
  }
  $retval .= '</tr>';
}
$retval .= '</table>';

echo $retval;

The other method is to echo each line as the code comes to it:

<?php
$data['category']['parts']; // format of the data

echo '<table>';
foreach($data as $category) {
  echo '<tr>';
  foreach($category as $data) {
    echo '<td>'.$data.'</td>'
  }
  echo '</tr>';
}
echo '</table>';

Which of the two methods is more efficient, in terms of processor/memory usage, and also for processing speed? Is there actually a real difference, rather than just a question of style?

Answer 1

My shot is: whatever you find more readable. Impact on performance is so small that probably you won't see any difference.

However, if you really care, echo should be faster (nothing better than a performance test on your specific scenario) because string concatenation will resize retval multiple times (and this will impact performance).

Even better you should avoid concatenation also in your echo:

<?php
$data['category']['parts']; // format of the data

echo '<table>';
foreach($data as $category) {
  echo '<tr>';
  foreach($category as $data) {
    echo '<td>', $data, '</td>';
  }
  echo '</tr>';
}
echo '</table>';

Do you want to do better? Just construct your own string builder object (but, honestly, gain is so small that you should seriously consider if worth your effort).