the test was completed

index.php

 <?php
 $start = microtime(true);
+
 /**
  * "The Happy Tickets"
  *
- * host/?first=000001&end=124555
- *
- * @author   Alexandr Sitchenko <alexsitch@outlook.com>
+ * PHP >=7.2
+ * host/?first=000001&last=124555
+ * Statistical date: The sequence from 000 to 999 have 11*10 sums of number of each from 1 to 9
+ * The sequence from 00 to 99 have 11 sums of number of each from 1 to 9
+ * Example: There is number 3 is 37 sums in sequence from 566 to 222
+ * 566-222 = 344 = 3*100 + 4*10 + 4 -> 3*11 + 4*1 + 0 (4 !== 3) = 37
+ * @author Alexandr Sitchenko <alex.sit@outlook.com>
+ */
+
+/*
+ **************************
+ * Check input parameters *
+ **************************
  */
 
-if (!isset ($_GET['first'], $_GET['end'])) {
+if (!isset ($_GET['first'], $_GET['last'])) {
     exit('You haven`t passed the parameters.');
 }
-if (!ctype_digit($_GET['first']) || !ctype_digit($_GET['end'])) {
+if (!ctype_digit($_GET['first']) || !ctype_digit($_GET['last'])) {
     exit('You haven`t passed the parameters.');
 }
-if (strlen($_GET['first']) !== 6 || strlen($_GET['end']) !== 6) {
+if (strlen($_GET['first']) !== 6 || strlen($_GET['last']) !== 6) {
     exit('You must enter parameters in format 000XXX!!');
 }
-if (((int)$_GET['end'] - (int)$_GET['first']) <= 0) {
+
+/* the main parameters is set */
+$firstNumber = (int)$_GET['first'] < 999 ? 999 : (int)$_GET['first'];
+$lastNumber = (int)$_GET['last'];
+$range = $lastNumber - $firstNumber;
+
+if ($range <= 0) {
     exit('The first parameter must be less than the second!');
 }
-/* "The Happy Tickets" are not in sequence from 0 to 10 */
-if ((int)$_GET['end'] < 1001) {
-    exit('0 "The Happy Tickets" is in the indicated sequence ');
-}
 
-$current = (int)$_GET['end'];
 $ticketsHappy = 0;
-$currentLeft = intdiv($current, 1000);
-$currentRight = $current % 1000;
-
-$sumNumber = static function ($num) {
-    $sumCurrent = 0;
-    while ($num > 0) {
-        $sumCurrent += $num % 10;
-        $num = intdiv($num, 10);
-    }
-    if ($sumCurrent > 9) {
-        $sumCurrent = ($sumCurrent % 10) + intdiv($sumCurrent, 10);
+$message = ' "The Happy Tickets" is in the range';
+
+/* "The Happy Tickets" are not in sequence from 000001 to 001000 */
+if ($lastNumber < 1001) {
+    exit($ticketsHappy . $message);
+}
+
+/*
+ *****************************
+ * Block for set of function *
+ *****************************
+ */
+
+/*
+ * Sum of numeric in three-digit number
+ *
+ * @param int $num - three-digit number
+ * @return int - sum of numeric in input number
+ */
+$sumNumberMax3Numeric = static function (int $num): int {
+    $sum = (int)($num / 100) + (int)(($num % 100) / 10) + $num % 10;
+    if ($sum > 9) {
+        $sum = (int)(($sum % 100) / 10) + $sum % 10;
     }
-    return $sumCurrent;
+    return $sum;
+};
+
+/**
+ * "The Happy Tickets" is calculated into range without las ten
+ *
+ * number of Coincidences in 1000 = (int)($range / 1000 - 1) * 11 * 10;
+ * number of Coincidences in 100 = (int)(($range % 1000) / 100 ) * 11;
+ * number of Coincidences in 10 = (int)(($range % 100) / 10 );
+ *
+ * @param int $range
+ * @return int
+ */
+$numberCoincidences10 = static function (int $range): int {
+    return (int)($range / 1000 ) * 11 * 10 + (int)(($range % 1000) / 100) * 11 + (int)(($range % 100) / 10);
 };
 
-while ($currentLeft > 0) {
-    $sumCurrentLeft = $sumNumber($currentLeft);
-    while ($currentRight >= 0) {
-        $sumCurrentRight = $sumNumber($currentRight);
-        if ($sumCurrentLeft === $sumCurrentRight ) {
-            ++$ticketsHappy;
+/**
+ * "The Happy Tickets" is calculated into las ten
+ *
+ * @param int $range
+ * @param int $lastNumber
+ * @return int
+ */
+$numberCoincidencesLast10 = static function (int $range, int $lastNumber) use ($sumNumberMax3Numeric): int {
+    $lastTen = $range % 10;
+    $startForCheck = $lastNumber - $lastTen;
+    $checkThousand = (((int)($lastNumber / 1000) - (int)($startForCheck / 1000)) === 1);
+
+    /* example if tickets are have a numeric from 003999 to 004001 */
+    $sumNumberLeftPart = $sumNumberMax3Numeric((int)($startForCheck / 1000));
+
+    $coincidencesLast10 = 0;
+    while ($startForCheck <= $lastNumber) {
+        $sumCurrent = $sumNumberMax3Numeric($startForCheck % 100);
+        if ($checkThousand && $sumCurrent === 0) {
+            $sumNumberLeftPart = $sumNumberMax3Numeric((int)($startForCheck / 1000));
         }
-        --$currentRight;
-    }
-    if ($currentLeft > 0) {
-        $currentRight = 999;
+        if ($sumNumberLeftPart === $sumCurrent) {
+            ++$coincidencesLast10;
+        }
+        ++$startForCheck;
     }
-    --$currentLeft;
-}
+    return $coincidencesLast10;
+};
+/*
+ ***************************************
+ * The end a block for set of function *
+ ***************************************
+ */
 
-echo $ticketsHappy;
+/**
+ * The calculate for "The Happy Tickets"
+ */
+$ticketsHappy = $numberCoincidences10($range) + $numberCoincidencesLast10($range, $lastNumber);
+echo $ticketsHappy . $message;
+
+/* time of script */
 echo '<br /><br />';
-echo 'Script execution time: ' . round(microtime(true) - $start, 4) . ' s.';
+echo 'Script execution time: ' . round(microtime(true) - $start, 4) . ' s.';
\ No newline at end of file
+
+/*
+ *********************
+ * The block of test *
+ *********************
+ */
+echo '<h1>Test:</h1>';
+/**
+ * @param int $firstNumberTest
+ * @param int $lastNumberTest
+ * @param int $happyTicketsMustBe
+ */
+$test = static function (int $firstNumberTest, int $lastNumberTest, int $happyTicketsMustBe)
+use ($numberCoincidences10, $numberCoincidencesLast10): void {
+    $rangeTest = $lastNumberTest - $firstNumberTest;
+    $testResult = 'False';
+    $ticketTest = $numberCoincidences10($rangeTest) + $numberCoincidencesLast10($rangeTest, $lastNumberTest);
+    if ($ticketTest === $happyTicketsMustBe) {
+        $testResult = 'True';
+    }
+    echo 'There are(is) a ' . $happyTicketsMustBe . ' "The Happy Tickets"  
+        must be in range from ' . $firstNumberTest . ' to ' . $lastNumberTest .
+        ' - ' . $testResult;
+    echo '<br /><br />';
+};
+
+$test(999, 1001, 1);
+$test(9999, 10001, 2);
\ No newline at end of file