Comparing Three PHP Methods to Multiply an Integer by 1000: String Concatenation, Direct Multiplication, and 1024‑Minus‑24 Approximation

How to Efficiently Multiply an Integer by 1000 in PHP

When asked to increase a positive integer by a thousand, the obvious human answer is to append three zeros; however, a programmer must consider the operation from a computational perspective.

The author first proposes two straightforward solutions:

Solution 1: Concatenate the string "000" to the integer (e.g., $result = (int)($integer . '000');).

Solution 2: Directly multiply the integer by 1000 (e.g., $result = $integer * 1000;).

A colleague suggests a more “clever” approach using binary arithmetic: Result = X * 1024 - X * 24. The reasoning is that multiplying by 1024 (2¹⁰) can be performed with bit‑shifts, which should be faster than adding a long series of powers of two.

Benchmark Experiment

To verify the performance of the three methods, the author writes a Laravel script that runs each method ten million times and records the elapsed time using Carbon::now()->getPreciseTimestamp(). The benchmark code is:

$headers = ['次数', '方案1：拼接法', '方案2：乘1000', '方案3：乘以 1024'];
$data = [];
// Method 1 – string concatenation
for ($count = 0; $count < 3; $count++) {
    $start = Carbon::now()->getPreciseTimestamp();
    for ($i = 0; $i < 10000000; $i++) {
        $integer = rand(1, 999);
        $result = (int)($integer . '000');
    }
    $end = Carbon::now()->getPreciseTimestamp();
    $data[$count][] = ($end - $start) / 1000000 . '秒';
}
// Method 2 – direct multiplication
for ($count = 0; $count < 3; $count++) {
    $start = Carbon::now()->getPreciseTimestamp();
    for ($i = 0; $i < 10000000; $i++) {
        $integer = rand(1, 999);
        $result = $integer * 1000;
    }
    $end = Carbon::now()->getPreciseTimestamp();
    $data[$count][] = ($end - $start) / 1000000 . '秒';
}
// Method 3 – 1024‑minus‑24 formula
for ($count = 0; $count < 3; $count++) {
    $start = Carbon::now()->getPreciseTimestamp();
    for ($i = 0; $i < 10000000; $i++) {
        $integer = rand(1, 999);
        $result = $integer * 1024 - $integer * 24;
    }
    $end = Carbon::now()->getPreciseTimestamp();
    $data[$count][] = ($end - $start) / 1000000 . '秒';
}
$this->table($headers, $data);

After multiple runs, the author observes a stable result: the concatenation method is the slowest, the direct multiplication is the fastest, and the 1024‑minus‑24 formula is unexpectedly slower than the simple multiplication.

Analysis of the Results

String concatenation requires converting the integer to a string, appending three characters, and converting back to an integer, which adds considerable overhead compared to pure arithmetic.

The binary‑based formula, while theoretically leveraging faster bit‑shift operations, still performs two multiplications and a subtraction in PHP’s interpreted environment, which makes it slower than a single multiplication by 1000.

The discussion also touches on language differences: PHP, being an interpreted language, may not optimize the 1024‑minus‑24 expression as a compiled language like C++ would, leading to the observed performance gap.

Overall, the experiment demonstrates that for this specific task, the simplest arithmetic operation ( $integer * 1000) provides the best performance in PHP.