Performance‑Optimized PHP: Faster Alternatives for Duplicates, Random Selection, Alphanumeric Checks, and Substring Replacement

1. Remove Duplicates

When you have a large array with many duplicate values and need a unique‑value array, the usual approach is array_unique($array). A faster alternative is array_keys(array_flip($array)). In a test with over 4 million elements and 3 million duplicates, array_unique took 787.31 ms while the alternative completed in 434.03 ms, roughly 1.8× faster (44.87 % faster on average).

2. Get a Random Array Record

The conventional function array_rand($array) selects a random key. An alternative is $array[mt_rand(0, count($array) - 1)]. With a 5‑million‑element array, array_rand required 25.99 µs, whereas the mt_rand method needed only 0.95 µs—about 27.3× faster (96.33 % faster on average). The speed gain stems from the Mersenne Twister implementation used by mt_rand, which has been the default randomizer since PHP 7.1.

3. Test Alphanumeric Characters

To verify that a string contains only letters and numbers, the common solution is preg_match('/^[a-zA-Z0-9]+$/', $string). The faster alternative is ctype_alnum($string). In a benchmark with over 100 k mixed strings, preg_match took 15.39 ms while ctype_alnum finished in 2.06 ms—approximately 7.5× faster (86.59 % faster on average). The same improvement applies to ctype_alpha() and ctype_digit().

4. Replace Substrings

The typical call str_replace('a', 'b', $string) can be replaced by strtr($string, 'a', 'b'). Testing on an array of 5 million random strings, str_replace required 676.59 ms, while strtr completed in 305.59 ms—about 2.2× faster (54.83 % faster on average).

Other Performance Improvements

Prefer JSON over XML.

Declare variables outside loops instead of inside each iteration.

Avoid function calls in loop headers (e.g., for ($i = 0; $i < count($array); $i++)).

Reset memory‑consuming variables when possible.

Prefer switch statements over multiple if checks.

Use require/include instead of require_once/include_once when opcode caching is enabled.

Even on PHP 7.4, which is already faster than earlier versions, these alternatives can noticeably reduce script execution time. The full test suite is available in the devmount/faster-php repository, and the measurements were taken with Bart van Hoekelen’s benchmarking tool.