How Can I Optimally Merge Two Flat Arrays with Alternating Values in PHP?

Merging Flat Arrays with Alternating Values Optimally

In situations where performance is crucial, you may encounter the need to merge two flat arrays of equal size, alternating their values. While a simple loop that iterates over the arrays can achieve this, it leaves room for potential performance optimization.

Native Solution

One way to merge the arrays efficiently uses a precalculated count. Here's the improved PHP code:

$count = count($a1);
for ($i = 0; $i < $count; $i++) {
    $newArray[] = $a1[$i];
    $newArray[] = $a2[$i];
}

Benchmark Comparison

To demonstrate the performance difference, we ran benchmarks with the original and updated code:

$a1 = array(0,1,2);
$a2 = array(3,4,5);

$start = microtime(TRUE);

for($t = 0; $t < 100000; $t++)
{
    $newArray = array();
    $count = count($a1);
    for ($i = 0; $i < $count; $i++)
    {
        $newArray[] = $a1[$i];
        $newArray[] = $a2[$i];
    }
}
echo  round(microtime(TRUE) - $start, 2); # 0.6

$a1 = array(0,1,2);
$a2 = array(3,4,5);

$start = microtime(TRUE);

for($t = 0; $t < 100000; $t++)
{
    $newArray = array();
    for ($i = 0; $i < count($a1); $i++) // count() inside loop
    {
        $newArray[] = $a1[$i];
        $newArray[] = $a2[$i];
    }
}
echo  round(microtime(TRUE) - $start, 2); # 0.85

The results show that pre-calculating the array size using count() offers a noticeable speed improvement. By avoiding repetitive counting, the optimized code operates significantly faster.

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