能否筛选数组中第3、4位等于指定子串的元素？

Absolutely, you can easily achieve this using PHP's array_filter() function paired with substr() to check the target substring. Here's a straightforward implementation:

$str = "CD";
$arr = ["ABCDE", "BCDEF", "BACDF","ACDLK"];

// Filter the array to match our criteria
$result = array_filter($arr, function($element) use ($str) {
    // Grab the 3rd and 4th characters (1-based index) → translates to 0-based index 2, length 2
    return substr($element, 2, 2) === $str;
});

// Optional: Reset array keys to start from 0 (removes original input keys)
$result = array_values($result);

print_r($result);

Output: #

Array
(
    [0] => ABCDE
    [1] => BACDF
)

Breakdown of how it works: #

• array_filter() loops through each element in your array and retains only those elements where the callback function returns true.
• substr($element, 2, 2) extracts the substring starting at 0-based index 2 (which is the 3rd character in 1-based counting) and grabs the next 2 characters (covering the 3rd and 4th positions you need).
• The use ($str) clause lets us access the target string inside the anonymous callback function to compare against.
• array_values() is optional but helpful if you want a clean, re-indexed array instead of keeping the original keys from the input array.

This method is efficient, readable, and directly meets your requirement of matching the specific substring positions.

内容的提问来源于stack exchange，提问作者p.Soni