PHP Examples

PHP Program - Reverse digits of a given Integer

In PHP, the reverse of a given integer can be found out by using below mentioned methods.

Method 1: Using iteration

The method involves the following steps:

Input: MyNum
Step 1: Initialize the RevNum = 0
Step 2: Iterate over MyNum while it is greater than zero.
   Step 2a: Calculate remainder of MuNum / 10
   Step 2b: Update RevNum by RevNum * 10 + remainder
   Step 2c: Update MyNum by (int)MyNum / 10
Step 3: Return RevNum

Example:

Input: 564

RevNum: 0
Iteration 1: 
    Remainder: 564 % 10 = 4
    RevNum: 0 * 10 + 4 = 4
    MyNum: 564 / 10 = 56

Iteration 2: 
    Remainder: 56 % 10 = 6
    RevNum: 4 * 10 + 6 = 46
    MyNum: 56 / 10 = 5

Iteration 3: 
    Remainder: 5 % 10 = 5
    RevNum: 46 * 10 + 5 = 465
    MyNum: 5 / 10 = 0

return RevNum = 465

The below block of code shows the implementation of above concept:

<?php
function reverse($MyNum){
  $RevNum = 0;
  $remainder;

  while($MyNum > 1){
    $remainder = $MyNum % 10;
    $MyNum = (int)$MyNum / 10;
    $RevNum = $RevNum * 10 + $remainder;
  }
  return $RevNum;
}

$x = 1285;
$y = 4567;
echo "Reverse of $x is: ".reverse($x);
echo "\nReverse of $y is: ".reverse($y);
?>

The above code will give the following output:

Reverse of 1285 is: 5821
Reverse of 4567 is: 7654

Method 2: Using Recursion

The above result can also be achieved using recursive function. Consider the example below:

<?php
$RevNum = 0;
$base = 1;

function reverse($MyNum){
  global $RevNum;
  global $base;

  if($MyNum > 1){
    reverse((int)$MyNum/10);
    $RevNum += $MyNum % 10 * $base;
    $base *= 10;
  }
  return $RevNum;
}

$x = 7902;
echo "Reverse of $x is: ".reverse($x);
?>

The above code will give the following output:

Reverse of 7902 is: 2097

PHP Program - Reverse digits of a given Integer

Method 1: Using iteration

Example:

Method 2: Using Recursion

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