I want to write an application that reverses all the words of input text, but all non-letter symbols should stay in the same places.

What I already have:

function reverse($string)
{
    $reversedString = '';

    for ($position = strlen($string); $position > 0; $position--) {
        $reversedString .= $string[$position - 1]; //.= - concatenation assignment, привязывает b to a;
      
    }
    return $reversedString;
}

$name = 'ab1 ab2';
print_r(reverse($name));

And how to write a fucntion, that return text without affecting any special characters? Output should be: "ab1 ab2" => "ba1 ba2"

CodePudding user response：

preg_replace_callback() is the perfect, native, one-liner for this task.

Code: (Demo)

$name = 'ab1 ab2';

echo preg_replace_callback('/[a-z] /i', fn($m) => strrev($m[0]), $name);
// ba1 ba2

Match one or more letters, replace each sequence of letters with the reversed version of itself.

CodePudding user response：

If I understood your problem correctly, then the solution below will probably be able to help you. This solution is not neat and not optimal, but it seems to work:

function reverse(string $string): string
{
    $reversedStrings = explode(" ", $string);

    foreach ($reversedStrings as &$word) {
        $chars = mb_str_split($word, 1);
        $filteredChars = [];
        foreach (array_reverse($chars) as $char) {
            if (ctype_alpha($char)) {
                $filteredChars[] = $char;
            }
        }
        foreach ($chars as &$char) {
            if (!ctype_alpha($char)) {
                continue;
            }
            $char = array_shift($filteredChars);
        }
        $word = implode("", $chars);
    }

    return implode(" ", $reversedStrings);
}

$name = "ab1 ab2 ab! ab. Hello!789World! qwe4rty5";
print_r(reverse($name)); // => "ba1 ba2 ba! ba. dlroW!789olleH! ytr4ewq5"

In the example, non-alphabetic characters do not change their position within the word. Example: "Hello!789World! qwe4rty5" => "dlroW!789olleH! ytr4ewq5".

CodePudding user response：

STEPS

1. Filter alphabetic $aplha and non-alphabetic characters $nonAlpha.
2. Reverse the alphabetic characters $reversed.
3. Push/insert the non-alphabetic characters $nonAlpha into the $reversed array while preserving the original non-alphabetic positions.

function strReverse(string $text): string
{
    $nonAlpha = [];
    $alpha = [];

    $mbStrSplit = mb_str_split($text);

    array_walk($mbStrSplit, function ($v, $k) use (&$nonAlpha, &$alpha) {

        if (mb_ereg_match("[^a-z]", $v, "i")) {
            $nonAlpha[$k] = $v;
        } else {
            $alpha[] = $v;
        }

    });

    $reversed = array_reverse($alpha);

    array_walk($nonAlpha, function ($v, $k) use (&$reversed) {
        array_splice($reversed, $k, 0, $v);
    });

    return implode("", $reversed);

}

var_export(strReverse("ab1 ab2")); // "ba1 ba2"
var_export(strReverse("ab1baa")); // "aa1bba"