Test task

<?php

/**
 *  Test tasks solving by Ruslan <retratserif@gmail.com> for cloud-team.ru
 *  Version 2
 */

// Task 1: Strings

/**
 * Task 1.1
 * Count word occurrence. Alternative realisation using preg_split
 * @param string $string input string.
 * @param string $word   word to count
 * @return int.
 */
function wordsCount(string $string, string $word)
{
    $word = mb_strtolower($word);
    $string = mb_strtolower($string);

    // Get list of words.
    $matches = usplit($string);

    // Get words stats.
    $result = array_count_values($matches);

    // Return stat for requested word.
    return $result[$word];
} // wordsCount()

/**
 * Task 1.2
 * Compare strings.
 * @param string $str1  Input string 1.
 * @param string $str2  Input string 2.
 * @return bool
 */
function wordsOrderDiffers(string $str1, string $str2)
{
    $str1 = mb_strtolower($str1);
    $str2 = mb_strtolower($str2);

    // convert strings to list of words
    $words1 = usplit($str1);
    $words2 = usplit($str2);

    // Return compare result.
    return $words1 != $words2;
}

/**
 * Helper function to split string to words with unicode support.
 * @param string $string  Input string.
 * @return array          Array of words.
 */
function usplit(string $string)
{
    $matches = null;
    preg_match_all('/\p{L}+/u', $string, $matches);
    return $matches[0];
}


// Task 2: Dates

/**
 * Task 2.1
 * Return current date in format 2017/04/20 - 09:25.
 * @return string
 */
function myTimestamp()
{
    return date('Y/m/d - H:i');
} // mytimestamp()

/**
 * Task 2.2
 * Count week days
 * @param int $weekday weekday to count.
 * @param int $year    year to count weekdays in.
 * @param return int
 */
function countWeekDays(int $weekday, int $year)
{
    if ($weekday > 6 || $weekday < 0)
        throw new Error('Weekday must be from 0 (sunday) to 6 (saturday).');

    // UNIX timestamp of January 1
    $startTime = mktime(0, 0, 0, 1, 1, $year);
    // UNIX timestamp of December 31
    $endTime = mktime(0, 0, 0, 12, 31, $year);

    $day = 60 * 60 * 24;

    $count = 0;

    for ($i = $startTime; $i <= $endTime; $i+=$day)
    {
        $date = getDate($i);
        if ($date['wday'] == $weekday)
            $count++;
    }

    return $count;
} // countWeekDays()

/**
 * Task 2.3
 * Get next sunday timestamp.
 * @return string
 */
function nextSunday()
{
    $date = getdate();

    // Current day:
    $currentDay = $date['wday'];

    // offset to the sunday:
    $offsetDays = 7 - $currentDay;
    $offsetSeconds = $offsetDays * 24 * 60 * 60;

    // Next sunday in Unix format
    $nextSundayTime = time() + $offsetSeconds;

    $sundayDate = date('Y-m-d', $nextSundayTime);

    return $sundayDate;
} // nextSunday()


// Task 3: Arrays

/**
 * Task 3.1
 * Sort array by array
 * @param array $arr1  Array to sort.
 * @param array $arr2  Array to sort by.
 * @return array
 */
function sortArrayByArray(array $arr1, array $arr2)
{
    // Throw an error if wrong type of input.
    if (!is_array($arr1) || !is_array($arr2))
        throw new Error('This function accepts arrays only.');

    // Throw error if lengths of the arrays are not equal.
    if (count($arr1) != count($arr2))
        throw new Error('Input arrays must have equal length.');

    // Throw error if input arrays are not sequential.
    if (!isSeqArray($arr1) || !isSeqArray($arr2))
        throw new Error('Arrays must be sequential.');

    // Now create new sorted array.
    $newArr = array();
    foreach ($arr2 as $key)
    {
        $k = $key - 1;

        if(!isset($arr1[$k]))
            throw new Error("Key $key not exist, wrong data in array2.");

        $newArr[$k] = $arr1[$k];
    }

    return $newArr;

} // sortArrayByArray()

/**
 * Task 3.2
 * array_merge alalog.
 * @param array $arrays arrays to merge.
 * @return array  Merged array.
 */
function ArrayMerge(...$arrays)
{
    // Get first array.
    $array1 = array_shift($arrays);

    if (!is_array($array1))
        throw new Exception('ArrayMerge() accepts arrays only.');

    // Process each input array
    foreach($arrays as $arr)
    {
        if (!is_array($arr))
            throw new Exception('ArrayMerge() accepts arrays only.');

        foreach($arr as $k => $v)
        {
            if (is_integer($k))
                $array1[] = $v;
            else
                $array1[$k] = $v;
        }
    }

    return $array1;
} // ArrayMerge()

/**
 * Task 3.3
 * Sum all elements of multidimensional array
 * @param array $arr  Input array
 * @return int
 */
function sumArrayElements(array $arr)
{
    $sum = 0;

    // Walk through array (using recurse for multidimensional).
    foreach($arr as $val)
    {
        if (is_array($val))
        {
            if(!isSeqArray($val))
                throw new Error('This function supports sequentional arrays only.');

            $sum += sumArrayElements($val);
        }
        elseif (is_integer($val))
        {
            $sum += $val;
        }
        else
        {
            throw new Error('Input data must contain arrays of integers only. Multidimensional arrays also supported.');
        }
    }

    return $sum;
} // sumArrayElements()

/**
 * Task 3.4
 * Find equal values in arrays.
 * @param array $arrays
 * @return array
 */
function equalValuesOfArrays(...$arrays)
{
    $result = array();

    if (count($arrays) < 2)
        throw new Error('equalValuesOfArrays() expects at least 2 arguments.');

    foreach ($arrays as $array1)
    {
        foreach($arrays as $array2)
        {
            if (!is_array($array2))
                throw new Error('equalValuesOfArrays() accepts arrays only.');

            if ($array1 == $array2)
                continue;

            // Find intersect
            $intersectArray = array_intersect($array1, $array2);

            // Store only unique values.
            $diffArray = array_diff($intersectArray, $result);
            $result = array_merge($result, $diffArray);
        }
    }

    return $result;
} // equalValuesOfArrays()

/**
 * Task 4:
 * Factorial:
 * @param int $n  facrorial size
 * @return int
 */
function factorial(int $n)
{
    if ($n > 1)
        return $n * factorial($n-1);
    else
        return 1;
}


/**
 * Helper function.
 * Check if array is sequential.
 * @param array $arr  Array to check.
 * @return bool
 */
function isSeqArray(array $arr)
{
    return array_keys($arr) === range(0, count($arr) - 1);
}


// Testing:
function test()
{
    echo "Task 1.1:\n";
    echo "  WordsCount('Никогда не qwerty,, (ыафыва)!!никогда', 'никогда'):
    should return 2: " . wordsCount('Никогда не qwerty,, (ыафыва)!!никогда', 'никогда');
    echo "\n\n";

    echo "Task 1.2:\n";
    echo "  WordsOrderDiffers('Мама мыла раму', 'Мыла раму мама'): " . var_export(WordsOrderDiffers('Мама мыла раму', 'Мыла раму мама'), true);
    echo "\n";

    echo "  WordsOrderDiffers('Мама мыла раму', 'мама мыла раму'): " . var_export(WordsOrderDiffers('Мама мыла раму', 'мама мыла раму'), true);
    echo "\n\n";

    echo "Task 2.1:\n";
    echo "  myTimestamp(): " . myTimestamp();
    echo "\n\n";

    echo "Task 2.2\n";
    echo "  countWeekDays(1, 2019): Count mondays of this year: " . countWeekDays(1, 2019);
    echo "\n";
    echo "  countWeekDays(5, 2019): Count fridays of this year: " . countWeekDays(5, 2019);
    echo "\n\n";

    echo "Task 2.3:\n";
    echo "  nextSunday(): " . nextSunday();
    echo "\n\n";

    echo "Task 3.1:\n";
    echo "  SortArrayByArray(['x', 'm', 'g', 's', 'a'], [3, 5, 1, 4, 2]):
" . var_export(SortArrayByArray(['x', 'm', 'g', 's', 'a'], [3, 5, 1, 4, 2]), true);
    echo "\n\n";

    echo "Task 3.2:\n";
    echo "  ArrayMerge([1, 2, 'a' => 'A', 3], [4, 5, 'b' => 'B'], [6, 'a' => 'AA', 7]):
" . var_export(ArrayMerge([1, 2, 'a' => 'A', 3], [4, 5, 'b' => 'B'], [6, 'a' => 'AA', 7]), true);
    echo "\n\n";

    echo "Task 3.3:\n";
    echo "  sumArrayElements([ [12, 18 ], 40, [ 4, 6, [ 10 ] ] ]): " .
    sumArrayElements([ [12, 18 ], 40, [ 4, 6, [ 10 ] ] ]);
    echo "\n\n";

    echo "Task 3.4:\n";
    echo "  equalValuesOfArrays([1, 5, 6, 8], [2, 3, 4, 5, 4], [10, 3, 12, 7]): " .
    var_export(equalValuesOfArrays([1, 5, 6, 8], [2, 3, 4, 5, 4], [10, 3, 12, 7]), true);
    echo "\n\n";

    echo "Task 4:\n";
    echo "  factorial(5): " . factorial(5);
    echo "\n";
} // test()

// Run tests if called with --test arg.
if (count($argv) > 1 && $argv[1] == '--test')
    test();