# PHP Challenges: Exercises, Practice, Solution

## PHP Challenges - 1 [25 exercises with solution]

[An editor is available at the bottom of the page to write and execute the scripts.]

1. Write a PHP program to check whether a given positive integer is a power of two. Go to the editor
Input : 4
Output :4 is power of 2
Click me to see the sample solution

2. Write a PHP program to check whether a given positive integer is a power of three. Go to the editor
Input : 9
Output : 9 is power of 3
Click me to see the sample solution

3. Write a PHP program to check whether a given positive integer is a power of four. Go to the editor
Input : 4
Output : 4 is power of 4
Click me to see the sample solution

4. Write a PHP program to check whether an integer is the power of another integer. Go to the editor
Input : 16, 2
Output : 16 is power of 2
Example: For x = 16 and y = 2 the answer is "true", and for x = 12 and y = 2 "false"
Click me to see the sample solution

5. Write a PHP program to find a missing number(s) from an array.Go to the editor
Input : 1,2,3,6,7,8
Output : Array
(
 => 4
 => 5
)
Click me to see the sample solution

6. Write a PHP program to find three numbers from an array such that the sum of three consecutive numbers equal to zero.Go to the editor
Input : (-1,0,1,2,-1,-4)
Output : Array
(
 => -1 + 0 + 1 = 0
)
Click me to see the sample solution

7. Write a PHP program to find three numbers from an array such that the sum of three consecutive numbers equal to a given number. Go to the editor
Input : (array(2, 7, 7, 1, 8, 2, 7, 8, 7), 16))
Output : Array
(
 => 2 + 7 + 7 = 16
 => 7 + 1 + 8 = 16
)
Click me to see the sample solution

8. Write a PHP program to compute and return the square root of a given number. Go to the editor
Input : 16
Output : 4
Click me to see the sample solution

9. Write a PHP program to find a single number in an array that doesn't occur twice. Go to the editor
Input : array(5, 3, 4, 3, 4)
Output : Array
(
 => 5
 => 3
 => 4
 => 3
 => 4
)
Single Number: 5
Click me to see the sample solution

10. Write a PHP program to find the single element in an array where every element appears three times except for one.Go to the editor
Input : array(5, 3, 4, 3, 5, 5, 3)
Output : Array
(
 => 5
 => 3
 => 4
 => 3
 => 5
 => 5
 => 3
)
Single Number: 4
Click me to see the sample solution

11. Write a PHP program to find the single element appears once in an array where every element appears twice except for one. Go to the editor
Input : array(5, 3, 0, 3, 0, 5, 7, 7, 9)
Output : 9
Click me to see the sample solution

12. Write a PHP program to add the digits of a positive integer repeatedly until the result has a single digit.Go to the editor
For example given number is 59, the result will be 5.
Input : 48
Output : 3
Step 1: 5 + 9 = 14
Step 1: 1 + 4 = 5
Click me to see the sample solution

13. Write a PHP program to reverse the digits of an integer.Go to the editor
Sample :
x = 234, return 432
x = -234, return -432
Click me to see the sample solution

14. Write a PHP program to reverse the bits of an integer (32 bits unsigned). Go to the editor

Input : 1234
Output: 1260388352
For example, 1234 represented in binary as 10011010010 and returns 1260388352 which represents in binary as 1001011001000000000000000000000.
Click me to see the sample solution

15. Write a PHP program to check whether a sequence of numbers is an arithmetic progression or not. Go to the editor
In mathematics, an arithmetic progression or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant.
Input : array(5, 7, 9, 11)
Output : An arithmetic sequence
For example, the sequence 5, 7, 9, 11, 13, 15 ... is an arithmetic progression with common difference of 2.
Click me to see the sample solution

16. Write a PHP program to check whether a sequence of numbers is a geometric progression or not. Go to the editor
Input : array(2, 6, 18, 54)
Output : Geometric sequence
In mathematics, a geometric progression or geometric sequence, is a sequence of numbers where each term after the first is found by multiplying the previous one by a fixed, non-zero number called the common ratio. For example, the sequence 2, 6, 18, 54, ... is a geometric progression with common ratio 3. Similarly, 10, 5, 2.5, 1.25, ... is a geometric sequence with common ratio 1/2.
Click me to see the sample solution

17. Write a PHP program to compute the sum of the two reversed numbers and display the sum in reversed form. Go to the editor
Input : 13, 14
Output : 72
Note : The result will not be unique for every number for example 31 is a reversed form of several numbers of 13, 130, 1300 etc. Therefore all the leading zeros will be omitted.
Click me to see the sample solution

18. Write a PHP program where you take any positive integer n, if n is even, divide it by 2 to get n / 2. If n is odd, multiply it by 3 and add 1 to obtain 3n + 1. Repeat the process until you reach 1. Go to the editor
Input : 12
Output : Array
(
 => 12
 => 6
 => 3
 => 10
 => 5
 => 16
 => 8
 => 4
 => 2
 => 1
)
According to Wikipedia the Collatz conjecture is a conjecture in mathematics named after Lothar Collatz, who first proposed it in 1937. The conjecture is also known as the 3n + 1 conjecture.
The conjecture can be summarized as follows. Take any positive integer n. If n is even, divide it by 2 to get n / 2. If n is odd, multiply it by 3 and add 1 to obtain 3n + 1. Repeat the process (which has been called "Half Or Triple Plus One") indefinitely. The conjecture is that no matter what number you start with, you will always eventually reach 1.
Example :
For instance, starting with n = 12, one gets the sequence 12, 6, 3, 10, 5, 16, 8, 4, 2, 1.
n = 19, for example, takes longer to reach 1: 19, 58, 29, 88, 44, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8, 4, 2, 1.
Click me to see the sample solution

19. Write a PHP program to check whether a given number is an ugly number. Go to the editor
Input : 12
Output :12 is an Ugly number
Ugly numbers are positive numbers whose only prime factors are 2, 3 or 5. The sequence 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, ...
shows the first 10 ugly numbers.
Note: 1 is typically treated as an ugly number.
Click me to see the sample solution

20. Write a PHP program to get the Hamming numbers upto a given numbers also check whether a given number is an Hamming number. Go to the editor
Input : 1
Output : Hamming Number
In mathematics, an arithmetic progression or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant.
For example, the sequence 5, 7, 9, 11, 13, 15 ... is an arithmetic progression with common difference of 2.
Click me to see the sample solution

21. Write a PHP program to check whether a given string is an anagram of another given string. Go to the editor
Input : ('anagram','nagaram')
Output : These two strings are anagram
According to Wikipedia, an anagram is direct word switch or word play, the result of rearranging the letters of a word or phrase to produce a new word or phrase, using all the original letters exactly once; for example, the word anagram can be rearranged into nag-a-ram.
Click me to see the sample solution

22. Write a PHP program to push all zeros to the end of an array. Go to the editor
Input : array(0,2,3,4,6,7,10)
Output : Array
(
 => 2
 => 3
 => 4
 => 6
 => 7
 => 10
 => 0
)
Click me to see the sample solution

23. Write a PHP program to find majority element in an array. Go to the editor
Input : array(1, 2, 3, 4, 5, 5, 5, 5, 5, 5, 6)
Output : 5
Note: The majority element is the element that appears more than n/2 times where n is the number of elements in the array.
Click me to see the sample solution

24. Write a PHP program to find the length of the last word in a string. Go to the editor
Input : PHP Exercises
Output : 9
Click me to see the sample solution

25. Write a PHP program to find the single number which occurs odd number of times and other numbers occur even number of times. Go to the editor
Input : 4, 5, 4, 5, 2, 2, 3, 3, 2, 4, 4
Output : 2
Click me to see the sample solution

PHP Code Editor:

More to Come !

Do not submit any solution of the above exercises at here, if you want to contribute go to the appropriate exercise page.

﻿

## PHP: Tips of the Day

PHP: How to get a variable name as a string in PHP?

You could use get_defined_vars() to find the name of a variable that has the same value as the one you're trying to find the name of. Obviously this will not always work, since different variables often have the same values, but it's the only way I can think of to do this.

Edit: get_defined_vars() doesn't seem to be working correctly, it returns 'var' because \$var is used in the function itself. \$GLOBALS seems to work so I've changed it to that.

```function print_var_name(\$var) {
foreach(\$GLOBALS as \$var_name => \$value) {
if (\$value === \$var) {
return \$var_name;
}
}

return false;
}
```

Edit: to be clear, there is no good way to do this in PHP, which is probably because you shouldn't have to do it. There are probably better ways of doing what you're trying to do.

Ref : https://bit.ly/37qFimU