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errors at huffmannode.php

PHP Warning: Creating default object from empty value in huffman-coding-php/huffmannode.php on line 30
PHP Warning: Creating default object from empty value in huffman-coding-php/huffmannode.php on line 95

git clone not runs

php tests.php

PHP Fatal error: require_once(): Failed opening required 'bit-util-php/bitstream.php' (include_path='.:/usr/share/php') in /home/peter/sandbox/huffman-coding-php/huffmancoding.php on line 2

suggestion to simplify and perhaps optimize

This code use build-in functions,

function Huffman_DicEncode($symb2freq) {
    // from https://rosettacode.org/wiki/Huffman_coding#PHP
    $heap = new SplPriorityQueue;
    $heap->setExtractFlags(SplPriorityQueue::EXTR_BOTH);
    foreach ($symb2freq as $sym => $wt)
        $heap->insert(array($sym => ''), -$wt);

    while ($heap->count() > 1) {
        $lo = $heap->extract();
        $hi = $heap->extract();
        foreach ($lo['data'] as &$x)
            $x = '0'.$x;
        foreach ($hi['data'] as &$x)
            $x = '1'.$x;
        $heap->insert($lo['data'] + $hi['data'],
                      $lo['priority'] + $hi['priority']);
    }
    $result = $heap->extract();
    return $result['data'];
}


function Huffman_compact2bin($txt,$base=36,$dic=NULL) {
    $s = '';
    $a = str_split($txt);
    $symb2freq = array_count_values($a);
    if ($dic===NULL)
        $dic = Huffman_DicEncode($symb2freq);
    foreach($a as $c) $s.=$dic[$c];
    return  $s;
}