Efficiently displaying elements in an array

Question

I wrote the below method to list out the elements of an array, as well as adding the Oxford comma to the list if desired. However, my for-loop looks, perhaps, a little convoluted. Is there a better way to handle clearly both the Oxford comma and the ability to add a conjunction?

---

function listOut($array = array(), $oxford = false, $conjunction = 'and') {
 $count = is_array($array) ? count($array) : 0;
 switch($count) {
 case 0: // Either not an array or an empty array
 return '';
 case 1: // Only one element in the array, return it
 return $array[0];
 case 2: // Two elements; join them together with the conjunction
 return "{$array[0]} {$conjunction} {$array[1]}";
 default: // At least two elements, join with commas and conjunction
 $s = ", ";
 $t = "";
 for($i = 0; $i < $count; $i++) {
 // Add a conjunction if it's the last element in the array
 if($i + 1 === $count) {
 $s = $oxford ? $s . "$conjunction " : " $conjunction ";
 }
 // Only prepend comma if not the first element
 if($i > 0) { 
 $t .= $s;
 }
 // Add the element to the return string
 $t .= $array[$i];
 }
 return $t;
 }
}
$array1 = array('orange');
$array2 = array('white', 'gold');
$array3 = array('black', 'white', 'purple');
echo listOut($array1); // orange
echo listOut($array2); // white and gold
echo listOut($array3); // black, white and purple
echo listOut($array1, true); // orange
echo listOut($array2, true); // white and gold
echo listOut($array3, true); // black, white, and purple

Answer 1

You can effectively get rid of the switch statement as well as the is_array check in the count ternary if you do the check in the beginning (and exit early at that - so not wasting any cycles).

You can also get rid of

# Only prepend comma if not the first element
if($i > 0) { 
 $output .= $separator;
}

If you add a ternary concat to $output (at the expense of gaining 2 opcode calls over the if/else). This would be the function after cleaning it:

function listOut($array = array(), $oxford = false, $conjunction = 'and', $separator = ", ") {
 if(!is_array($array)){ # We're expecting an array 
 return false;
 }
 $count = count($array) ?: 0;
 $output = "";
 if($count == 2){ return implode(" $conjunction ", $array); }
 for($i = 0; $i < $count; $i++) {
 # Add a conjunction if it's the last element in the array
 if($i + 1 === $count) {
 $separator = $oxford ? $separator . "$conjunction " : " $conjunction ";
 }
 # Add the element to the return string
 $output .= ($i > 0 ? $separator : "") . $array[$i];
 }
 return $output;
}

and the test outputs:

$array = 'blue';
$array1 = array('orange');
$array2 = array('white', 'gold');
$array3 = array('black', 'white', 'purple');
$array4 = array('black', 'white', 'purple', 'gold');
echo listOut($array) . "<br>";
echo listOut($array1) . "<br>"; // orange
echo listOut($array2) . "<br>"; // white and gold
echo listOut($array3, true) . "<br>"; // black, white and purple
echo listOut($array4) . "<br>"; // black, white and purple

Results:

false
orange
white and gold
black, white, and purple
black, white, purple and gold

• Chris Forrence: I like a lot of the optimizations you've done! However, an Oxford comma would appear in a two-element array in this case ("white, and gold").
• jsanc623: Ah! Didn't test that. To solve that issue, just add if($count == 2){ return implode(" $conjunction ", $array); } after $count = count($array) ?: 0.
• Chris Forrence: Sounds good (and I actually made another modification to that by checking $count <= 2). Now I'll be able to list out items for perfectly peaceful purposes. Thank you!
• jsanc623: Good catch on the <=: exit early, exit often!