Morse Code Problem

morse-code-problem.php

function possibilities ($word) {
    $tree = [
        'children' => [
            [
                'symbol' => 'E',
                'children' => [
                    [
                        'symbol' => 'I',
                        'children' => [
                            [
                                'symbol' => 'S',
                                'children' => [],
                            ],
                            [
                                'symbol' => 'U',
                                'children' => [],
                            ],
                        ]
                    ],
                    [
                        'symbol' => 'A',
                        'children' => [
                            [
                                'symbol' => 'R',
                                'children' => [],
                            ],
                            [
                                'symbol' => 'W',
                                'children' => [],
                            ],
                        ]
                    ],
                ],
            ],
            [
                'symbol' => 'T',
                'children' => [
                    [
                        'symbol' => 'N',
                        'children' => [
                            [
                                'symbol' => 'D',
                                'children' => [],
                            ],
                            [
                                'symbol' => 'K',
                                'children' => [],
                            ],
                        ]
                    ],
                    [
                        'symbol' => 'M',
                        'children' => [
                            [
                                'symbol' => 'G',
                                'children' => [],
                            ],
                            [
                                'symbol' => 'O',
                                'children' => [],
                            ],
                        ]
                    ],
                ],
            ],
        ],
    ];
    
    $word = str_split($word);
    $possibilities = array();
    $cur = [$tree];
    for ($i = 0; $i < count($word); $i++) {
        $newCur = [];
        foreach ($cur as $_cur) {
            if ($word[$i] === '.') {
                $newCur[] = $_cur['children'][0];
                continue;
            }

            if ($word[$i] === '-') {
                $newCur[] = $_cur['children'][1];
                continue;
            }

            $newCur = array_merge($newCur, $_cur['children']);
        }
        
        $cur = $newCur;
    }
    
    foreach ($cur as $_cur) {
        $possibilities[] = $_cur['symbol'];
    }
    
    return $possibilities;
}