Palindrome problem solution.

pairPalindrome.php

declare(strict_types=1);

/**
 * Resolution to the problem:
 * Five Dwarves ( Gimli Fili Ilif Ilmig and Mark) met at the Prancing Pony and played 
 * a word game to determine which combinations of their names resulted in a palindrome.
 * Write a program in that prints out all of those combinations
 * */

//Class to pipe functions for better readability
class Piper {
  private $flow = [];
  protected $param;
  
  public function __construct($param = null){
    $this->param = $param;
  }
  
  //Pipe functions to be called
  public function pipe(callable $function) : Piper
  {
    $this->flow[] = $function;
    
    return $this;
  }
  
  //Saves the first param to use in the first function chain
  public function setParam($param){
    $this->param = $param;
    return $this;
  }
  
  //Call the chained functions and return the last result
  public function execute()
  {
    foreach ($this->flow as $flow) {
      $return = $flow($return ?? $this->param);
    }
    
    //Reset flow
    $this->flow = [];
    return $return;
  }
}

/**
 * Find palindrome pair function, receives a array with names and returns 
 * an associative array with the pairs
 * @param array $names - Names to find the palindrome pair
 **/
function findPalindrome(array $names = []) : array
{
  //Array to save names and reversed names
  $aNames = [];
  //Auxialiary array to save the found pairs
  $combinations = [];
  $arrSize = count($names);
  $pipe = new Piper();

  //Loop through names to find the pairs
  for ($i=0; $i < $arrSize; $i++){
    $name = strtolower($names[$i]);
    //$reversedName = strtolower(join("", array_reverse(str_split($name))));
    //Created the Pipe class just for better readability
    $reversedName = $pipe->setParam($name)->pipe('str_split')->pipe('array_reverse')->pipe('join')->pipe('strtolower')->execute();

    //If the actual name and the reversed name are not in the aNames push it
    //Using array and isset because its much faster than a linear search
    if( (!isset($aNames[$name]) && !isset($aNames[$reversedName]))){
      $aNames[$name] = $reversedName;
    }else{
      //Found the reversed name in the array which means the pair forms a palindrome
      //push name and the reversed name to the result array
      $combinations[$name] = $reversedName;
    }
  }
  
  return $combinations;
}

$names = ['Gimli', 'Fili', 'Ilif', 'Ilmig', 'Mark'];
print_r(findPalindrome($names));

//Testing performance
/*

function generateRandomString($length = 10) {
    $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    $charactersLength = strlen($characters);
    $randomString = '';
    for ($i = 0; $i < $length; $i++) {
        $randomString .= $characters[rand(0, $charactersLength - 1)];
    }
    return $randomString;
}

for($i=0; $i< 200000; $i++){
  $names[] = generateRandomString(5);
}

$start = microtime(true);
echo $start . PHP_EOL;
print_r(findPalindrome($names));
echo (microtime(true) - $start) . PHP_EOL;*/