Php Program to Move all zeroes to end of array

Given an array of random numbers, Push all the zero’s of a given array to the end of the array. For example, if the given arrays is {1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0}, it should be changed to {1, 9, 8, 4, 2, 7, 6, 0, 0, 0, 0}. The order of all other elements should be same. Expected time complexity is O(n) and extra space is O(1).
Example:

Input :  arr[] = {1, 2, 0, 4, 3, 0, 5, 0};
Output : arr[] = {1, 2, 4, 3, 5, 0, 0};

Input : arr[]  = {1, 2, 0, 0, 0, 3, 6};
Output : arr[] = {1, 2, 3, 6, 0, 0, 0};

There can be many ways to solve this problem. Following is a simple and interesting way to solve this problem. 
Traverse the given array ‘arr’ from left to right. While traversing, maintain count of non-zero elements in array. Let the count be ‘count’. For every non-zero element arr[i], put the element at ‘arr[count]’ and increment ‘count’. After complete traversal, all non-zero elements have already been shifted to front end and ‘count’ is set as index of first 0. Now all we need to do is that run a loop which makes all elements zero from ‘count’ till end of the array.
Below is the implementation of the above approach. 

PHP

<?php
// A PHP program to move all
// zeroes at the end of array

// Function which pushes all
// zeros to end of an array.
function pushZerosToEnd(&$arr, $n)
{
    // Count of non-zero elements
    $count = 0;

    // Traverse the array. If
    // element encountered is
    // non-zero, then replace
    // the element at index
    // 'count' with this element
    for ($i = 0; $i < $n; $i++)
        if ($arr[$i] != 0)
            // here count is incremented
            $arr[$count++] = $arr[$i];

    // Now all non-zero elements
    // have been shifted to front
    // and 'count' is set as index
    // of first 0. Make all elements
    // 0 from count to end.
    while ($count < $n)
        $arr[$count++] = 0;
}

// Driver Code
$arr = array(1, 9, 8, 4, 0, 0,
             2, 7, 0, 6, 0, 9);
$n = sizeof($arr);
pushZerosToEnd($arr, $n);
echo "Array after pushing all " .
     "zeros to end of array :
";

for ($i = 0; $i < $n; $i++)
echo $arr[$i] . " ";

// This code is contributed
// by ChitraNayal
?>

Output:

Array after pushing all zeros to end of array :
1 9 8 4 2 7 6 9 0 0 0 0

Time Complexity: O(n) where n is number of elements in input array.
Auxiliary Space: O(1)

Please refer complete article on Move all zeroes to end of array for more details!