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PHP Coding Questions

Write a PHP script to print the numbers from 1 to 100. But for multiples of three print "Fizz" instead of the number and for the multiples of five print "Buzz". For numbers that are multiples of both three and five print "FizzBuzz".

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for ($i = 1; $i <= 100; $i++) {
  if ($i % 15 == 0) {
    echo "FizzBuzz\n";
  } else if ($i % 3 == 0) {
    echo "Fizz\n";
  } else if ($i % 5 == 0) {
    echo "Buzz\n";
  } else {
    echo "$i\n";
  }
}

Write a PHP function to calculate the factorial of a number.

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function factorial($n) {
  if ($n == 0) {
    return 1;
  } else {
    return $n * factorial($n - 1);
  }
}
echo factorial(5); // Output: 120

Write a PHP program to find the second largest number in an array.

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function secondLargest($arr) {
  $first = $second = PHP_INT_MIN;
  for ($i = 0; $i < count($arr); $i++) {
    if ($arr[$i] > $first) {
      $second = $first;
      $first = $arr[$i];
    } else if ($arr[$i] > $second && $arr[$i] != $first) {
      $second = $arr[$i];
    }
  }
  return $second;
}
$arr = [10, 20, 30, 40, 50];
echo secondLargest($arr); // Output: 40

Write a PHP program to count the number of words in a string.

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function countWords($str) {
  $words = explode(' ', $str);
  return count($words);
}
$str = "This is a test string.";
echo countWords($str); // Output: 5

Write a PHP program to check whether a number is prime or not.

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function isPrime($n) {
  if ($n <= 1) {
    return false;
  }
  for ($i = 2; $i <= sqrt($n); $i++) {
    if ($n % $i == 0) {
      return false;
    }
  }
  return true;
}
echo isPrime(7); // Output: true

Write a PHP program to remove duplicates from an array.

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function removeDuplicates($arr) {
  return array_values(array_unique($arr));
}
$arr = [10, 20, 30, 20, 40, 10];
print_r(removeDuplicates($arr)); // Output: Array ( [0] => 10 [1] => 20 [2] => 30 [4] => 40 )

Write a PHP program to check whether a string is a palindrome or not.

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function isPalindrome($str) {
  $str = str_replace(' ', '', $str);
  $str = strtolower($str);
  return $str == strrev($str);
}
$str = "A man a plan a canal Panama";
echo isPalindrome($str); // Output: true

Write a PHP program to find the length of the longest consecutive sequence in an array.

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function longestConsecutive($arr) {
  $hash = array_flip($arr);
  $longest = 0;
  foreach ($arr as $num) {
    if (!isset($hash[$num-1])) {
      $current = $num;
      $length = 1;
      while (isset($hash[$current+1])) {
        $current++;
        $length++;
      }
      $longest = max($longest, $length);
    }
  }
  return $longest;
}
$arr = [100, 4, 200, 1, 3, 2];
echo longestConsecutive($arr); // Output: 4

Write a PHP program to find the largest sum of contiguous subarray in an array.

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function maxSubarraySum($arr) {
  $max = $current = $arr[0];
  for ($i = 1; $i < count($arr); $i++) {
    $current = max($arr[$i], $current + $arr[$i]);
    $max = max($max, $current);
  }
  return $max;
}
$arr = [-2,1,-3,4,-1,2,1,-5,4];
echo maxSubarraySum($arr); // Output: 6

Write a PHP program to find the missing number in an array of consecutive integers.

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function missingNumber($arr) {
  $n = count($arr) + 1;
  $sum = ($n * ($n + 1)) / 2;
  $sumArr = array_sum($arr);
  return $sum - $sumArr;
}
$arr = [1, 2, 4, 5, 6];
echo missingNumber($arr); // Output: 3

Write a PHP program to find the first non-repeating character in a string.

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function firstNonRepeatingChar($str) {
  $count = array_count_values(str_split($str));
  foreach ($count as $char => $num) {
    if ($num == 1) {
      return $char;
    }
  }
  return null;
}
$str = "leetcode";
echo firstNonRepeatingChar($str); // Output: "l"

Write a PHP program to find the maximum product of two integers in an array.

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function maxProduct($arr) {
  $max1 = $max2 = PHP_INT_MIN;
  $min1 = $min2 = PHP_INT_MAX;
  foreach ($arr as $num) {
    if ($num > $max1) {
      $max2 = $max1;
      $max1 = $num;
    } else if ($num > $max2) {
      $max2 = $num;
    }
    if ($num < $min1) {
      $min2 = $min1;
      $min1 = $num;
    } else if ($num < $min2) {
      $min2 = $num;
    }
  }
  return max($max1 * $max2, $min1 * $min2);
}
$arr = [-10,-10,5,2];
echo maxProduct($arr); // Output: 100

Write a PHP program to find the sum of all the numbers in a given array.

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function arraySum($arr) {
  return array_sum($arr);
}
$arr = [1, 2, 3, 4, 5];
echo arraySum($arr); // Output: 15

Write a PHP program to find the second largest number in an array of integers.

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function secondLargest($arr) {
  $max1 = $max2 = PHP_INT_MIN;
  foreach ($arr as $num) {
    if ($num > $max1) {
      $max2 = $max1;
      $max1 = $num;
    } else if ($num > $max2 && $num != $max1) {
      $max2 = $num;
    }
  }
  return $max2;
}
$arr = [1, 2, 3, 4, 5];
echo secondLargest($arr); // Output: 4

Write a PHP program to reverse a given string.

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function reverseString($str) {
  return strrev($str);
}
$str = "hello";
echo reverseString($str); // Output: "olleh"

Write a PHP program to check if a given string is a palindrome.

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function isPalindrome($str) {
  return $str == strrev($str);
}
$str1 = "racecar";
$str2 = "hello";
echo isPalindrome($str1); // Output: true
echo isPalindrome($str2); // Output: false

Write a PHP program to count the number of vowels in a given string.

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function countVowels($str) {
  return preg_match_all('/[aeiou]/i', $str);
}
$str = "hello world";
echo countVowels($str); // Output: 3

Write a PHP program to find the factorial of a given number.

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function factorial($n) {
  if ($n < 2) {
    return 1;
  }
  return $n * factorial($n - 1);
}
$n = 5;
echo factorial($n); // Output: 120

Write a PHP program to find the Fibonacci series up to a given number.

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function fibonacci($n) {
  $fib = [0, 1];
  for ($i = 2; $i <= $n; $i++) {
    $fib[$i] = $fib[$i-1] + $fib[$i-2];
  }
  return $fib;
}
$n = 10;
echo implode(", ", fibonacci($n)); // Output: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55

Write a PHP program to find the GCD (Greatest Common Divisor) of two numbers.

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function gcd($a, $b) {
  while ($b != 0) {
    $temp = $b;
    $b = $a % $b;
    $a = $temp;
  }
  return $a;
}
$a = 12;
$b = 18;
echo gcd($a, $b); // Output: 6

Write a PHP program to sort an array of integers in ascending order.

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function sortArray($arr) {
  sort($arr);
  return $arr;
}
$arr = [4, 2, 1, 3, 5];
echo implode(", ", sortArray($arr)); // Output: 1, 2, 3, 4, 5

Write a PHP program to remove all duplicate values from an array.

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function removeDuplicates($arr) {
  return array_unique($arr);
}
$arr = [1, 2, 1, 3, 2, 4, 5];
echo implode(", ", removeDuplicates($arr)); // Output: 1, 2, 3, 4, 5

Write a PHP program to find the intersection of two arrays.

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function arrayIntersection($arr1, $arr2) {
  return array_intersect($arr1, $arr2);
}
$arr1 = [1, 2, 3, 4, 5];
$arr2 = [3, 4, 5, 6, 7];
echo implode(", ", arrayIntersection($arr1, $arr2)); // Output: 3, 4, 5

Write a PHP program to find the union of two arrays.

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function arrayUnion($arr1, $arr2) {
  return array_unique(array_merge($arr1, $arr2));
}
$arr1 = [1, 2, 3, 4, 5];
$arr2 = [3, 4, 5, 6, 7];
echo implode(", ", arrayUnion($arr1, $arr2)); // Output: 1, 2, 3, 4, 5, 6, 7

Write a PHP program to find the first non-repeating character in a string.

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function firstNonRepeating($str) {
  $count = array_count_values(str_split($str));
  foreach ($count as $char => $freq) {
    if ($freq == 1) {
      return $char;
    }
  }
  return null;
}
$str = "hello world";
echo firstNonRepeating($str); // Output: "h"

Write a PHP program to find the maximum sum subarray in a given array of integers.

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function maxSubarraySum($arr) {
  $maxSum = $curSum = $arr[0];
  for ($i = 1; $i < count($arr); $i++) {
    $curSum = max($arr[$i], $curSum + $arr[$i]);
    $maxSum = max($maxSum, $curSum);
  }
  return $maxSum;
}
$arr = [-2, 1, -3, 4, -1, 2, 1, -5, 4];
echo maxSubarraySum($arr); // Output: 6

Write a PHP program to find the largest sum of two elements in a given array of integers.

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function maxSumOfTwo($arr) {
  sort($arr);
  return $arr[count($arr)-1] + $arr[count($arr)-2];
}
$arr = [4, 2, 1, 3, 5];
echo maxSumOfTwo($arr); // Output: 9

Write a PHP program to find the number of words in a given string.

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function countWords($str) {
  return str_word_count($str);
}
$str = "The quick brown fox jumps over the lazy dog.";
echo countWords($str); // Output: 9

Write a PHP program to reverse a given string.

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function reverseString($str) {
  return strrev($str);
}
$str = "Hello, world!";
echo reverseString($str); // Output: "!dlrow ,olleH"

Write a PHP program to check if a given string is a palindrome.

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function isPalindrome($str) {
  $str = strtolower(str_replace(" ", "", $str));
  return $str == strrev($str);
}
$str = "A man a plan a canal Panama";
echo isPalindrome($str) ? "Palindrome" : "Not a Palindrome"; // Output: Palindrome

Write a PHP program to count the frequency of each word in a given string.

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function countWordFrequency($str) {
  $count = array_count_values(str_word_count($str, 1));
  arsort($count);
  return $count;
}
$str = "The quick brown fox jumps over the lazy dog.";
print_r(countWordFrequency($str));
/* Output:
Array
(
    [the] => 2
    [brown] => 1
    [dog] => 1
    [fox] => 1
    [jumps] => 1
    [lazy] => 1
    [over] => 1
    [quick] => 1
)
*/

Write a PHP program to find the factorial of a given number.

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function factorial($n) {
  if ($n < 2) {
    return 1;
  }
  return $n * factorial($n-1);
}
$n = 5;
echo factorial($n); // Output: 120

Write a PHP program to find the sum of all the elements in a given array.

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function sumArray($arr) {
  return array_sum($arr);
}
$arr = [1, 2, 3, 4, 5];
echo sumArray($arr); // Output: 15

Write a PHP program to find the average of all the elements in a given array.

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function avgArray($arr) {
  return array_sum($arr) / count($arr);
}
$arr = [1, 2, 3, 4, 5];
echo avgArray($arr); // Output: 3

Write a PHP program to check if a given number is prime or not.

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function isPrime($n) {
  if ($n < 2) {
    return false;
  }
  for ($i = 2; $i <= sqrt($n); $i++) {
    if ($n % $i == 0) {
      return false;
    }
  }
  return true;
}
$n = 17;
echo isPrime($n) ? "Prime" : "Not a Prime"; // Output: Prime

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Introduction to PHP

Conditional Statements and Loops in PHP

PHP Arrays

PHP Functions

Forms in PHP

PHP File Handling

Object-Oriented Programming in PHP

PHP and MySQL

PHP Sessions and Cookies

PHP Security

Creating and Using PHP Libraries and Frameworks

PHP Debugging Techniques and Best Practices

Integrating PHP with Other Web Technologies

Creating and Consuming APIs with PHP

PHP Interview Questions

PHP Coding Questions

PHP Coding Questions