Question

I and Jim O’Brien have made two snippets of code, which do exactly the same. But which is faster?

(The code makes key-value pairs of even and odd numbers of the input array. If the input array is this:

Array(
    "thirteen",
    13,
    "seven",
    7,
    ...
)

then the output array will become this:

Array(
    "thirteen" => 13,
    "seven" => 7,
    ...
)

Snippet 1:

<?php

$output = array();
for ($i = 0; $i < count($input); $i++) {
    $output[$input[$i]] = $input[++$i];
}

?>

Snippet 2:

<?php

$output = array();
for ($i = 0; $i < count($input); $i += 2) {
    $output[$input[$i]] = $input[$i + 1];
}

?>

Which snippet is faster, and why?

Answer 1

The difference between them is insignificant compared to what you would save if you pre-computed count($input) instead of running it every time the loop comes around.

Just between the two you have given, the second is more readable and is the one I would choose. Efficiency-wise, it’s just not worth bothering about.