Unlock Powerful PHP Built‑in Functions: Levenshtein, Easter Date, Forks & More

1. Levenshtein

The levenshtein() function calculates the edit distance between two strings, i.e., the minimum number of insertions, deletions, or substitutions required to transform one string into another.

Example returning zero distance for identical strings:

levenshtein("PHP is awesome", "PHP is awesome"); // 0

When the strings differ, a larger distance is returned:

levenshtein("Dark colour schemes", "are awesome"); // 13

Levenshtein can also be used to compute a similarity percentage:

$s1 = 'Tinywan';
$s2 = 'ShaoBoWan';
$max_length = max(strlen($s1), strlen($s2));
$distance = levenshtein($s1, $s2);
$similarity_percent = (1 - $distance / $max_length) * 100;
echo $similarity_percent . '%';

This script outputs 22%, indicating a 22 % similarity between the two strings.

2. easter_date

The easter_date() function returns the Unix timestamp of Easter for a given year; if no year is supplied, the current year is used.

echo date('Y-m-d', easter_date(2023)); // 2023-04-08

3. forks (pcntl_fork)

When PHP is run via the CLI, the pcntl_fork() function (exposed through the pcntl extension) can create child processes, enabling concurrent execution.

Simple example of creating a child process with sockets:

function async(Process $process): Process {
    socket_create_pair(AF_UNIX, SOCK_STREAM, 0, $sockets);
    [$parentSocket, $childSocket] = $sockets;

    if (($pid = pcntl_fork()) == 0) {
        socket_close($childSocket);
        socket_write($parentSocket, serialize($process->execute()));
        socket_close($parentSocket);
        exit;
    }

    socket_close($parentSocket);
    return $process
        ->setStartTime(time())
        ->setPid($pid)
        ->setSocket($childSocket);
}

4. metaphone

The metaphone() function generates a phonetic key for a string, allowing words that sound alike to be compared.

metaphone("Light color schemes!"); // LFTKLRSXMS
metaphone("Light colour schemes!"); // LFTKLRSXMS

5. dns_get_record

dns_get_record()

retrieves DNS records for a domain, returning arrays that may include A, MX, NS, SOA, TXT, etc.

dns_get_record("ai.tinywan.com");

Sample output (truncated):

array(1) {
  [0]=>
  array(6) {
    ["host"]=> string(14) "ai.tinywan.com"
    ["class"]=> string(2) "IN"
    ["ttl"]=> int(3600)
    ["type"]=> string(3) "TXT"
    ["txt"]=> string(7) "RFC8482"
    ["entries"]=> array(2) {
      [0]=> string(7) "RFC8482"
      [1]=> string(0) ""
    }
  }
}

6. array_merge_recursive

This function merges one or more arrays recursively, combining values with the same keys into sub‑arrays.

Basic usage

$array1 = ['a' => ['b', 'c']];
$array2 = ['a' => ['d', 'e']];
$result = array_merge_recursive($array1, $array2);
print_r($result);

Result:

Array (
    [a] => Array (
        [0] => b
        [1] => c
        [2] => d
        [3] => e
    )
)

Handling of string keys

When the arrays share the same string key, their values are merged into a single array under that key.

$array1 = ['a' => 'apple', 'b' => 'banana'];
$array2 = ['a' => 'pear', 'c' => 'cherry'];
$result = array_merge_recursive($array1, $array2);
print_r($result);

Result:

Array (
    [a] => Array (
        [0] => apple
        [1] => pear
    )
    [b] => banana
    [c] => cherry
)

7. mail

The mail() function sends an email directly from a PHP script, returning TRUE on success.

$txt = "First line of text
Second line of text";
$txt = wordwrap($txt, 70);
mail("[email protected]", "开源技术小栈", $txt);

8. dl

The dl() function loads a PHP extension at runtime (available only in CLI builds).

if (!extension_loaded('sqlite')) {
    if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
        dl('php_sqlite.dll');
    } else {
        dl('sqlite.so');
    }
}

9. glob

glob()

returns an array of file or directory names matching a pattern.

print_r(glob(__DIR__ . "/*.md"));

Sample output:

Array (
    [0] => D:\work\docs\dev\other/account.md
    [1] => D:\work\docs\dev\other/changelog.md
    [2] => D:\work\docs\dev\other/meet.md
    [3] => D:\work\docs\dev\other/question.md
    [4] => D:\work\docs\dev\other/wechat.md
)

10. date_sun_info

date_sun_info()

returns an array with sunrise, sunset, and various twilight times for a given timestamp and geographic coordinates.

$sun_info = date_sun_info(strtotime("2024-01-01"), 31.7667, 35.2333);
foreach ($sun_info as $key => $val) {
    echo "$key: " . date("H:i:s", $val) . PHP_EOL;
}

Typical output:

sunrise: 04:38:51
sunset: 14:45:50
transit: 09:42:21
civil_twilight_begin: 04:12:07
civil_twilight_end: 15:12:34
nautical_twilight_begin: 03:41:45
nautical_twilight_end: 15:42:56
astronomical_twilight_begin: 03:12:03
astronomical_twilight_end: 16:12:38