How Can I Generate All Permutations of a String in PHP?

Permutations of a String in PHP

In PHP, generating all permutations of characters within a string involves an algorithm that systematically explores all possible combinations.

Backtracking Approach

One effective approach is backtracking. Here's the PHP implementation:

function permute($str,$i,$n) {
   if ($i == $n)
       print "$str\n";
   else {
        for ($j = $i; $j < $n; $j++) {
          swap($str,$i,$j);
          permute($str, $i+1, $n);
          swap($str,$i,$j); // backtrack.
       }
   }
}
function swap(&amp;$str,$i,$j) {
    $temp = $str[$i];
    $str[$i] = $str[$j];
    $str[$j] = $temp;
}   

$str = "hey";
permute($str,0,strlen($str)); // call the function.

Explanation

• The permute() function systematically explores all possible permutations.
• It recursively calls itself with increasing values of $i, the index of the character being swapped.
• The swap() function exchanges the characters at indices $i and $j.
• The recursion backtracks when the end of the string is reached, printing the resulting permutation.

Output

Executing the code with $str = "hey" produces the expected output:

hey
hye
ehy
eyh
yeh
yhe

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