In this tutorial, we will learn a simple sorting algorithm - Selection Sort.

Given a list of numbers as shown below, please sort them in ascending order.

```
$numbers = [21,25,100,98,89,77];
```

**Requirements**:

- You are required to use Selection Sort algorithm when sorting the numbers.
- You are required to implement the algorithm in PHP language.

Selection Sort works by maintaining a sorted sub-list, finding the smallest item from the master list and swap it to the last element of the sub-list until all items are sorted.

The sorted sub-list's length is increased by one, whereas the master list's length is shrunk by one after each swap.

Pseudocode of Selection Sort algorithm can be written as follows:

```
FOR each element of the master list indexed by i
Set current element of master list as the sub-list[i] element
Find the smallest item from the master list (staring from i)
Swap it with the last element of sub-list
END FOR
```

We need an outer FOR loop to iterate through the master list and an inner FOR loop to find the smallest item from the master list.

```
<?php
$masterList = [21, 25, 100, 98, 89, 77];
$subList = [];
for ($i = 0; $i < count($masterList); $i++) {
$subList[$i] = $masterList[$i];
// Find the smallest item
$smallestIndex = $i;
for ($j = $i; $j < count($masterList); $j++) {
if ($masterList[$j] < $masterList[$smallestIndex]) {
$smallestIndex = $j;
}
}
// Swap
$tmp = $subList[count($subList) - 1];
$subList[count($subList) - 1] = $masterList[$smallestIndex];
$masterList[$smallestIndex] = $tmp;
}
print_r($subList);
// Output:
/*
Array
(
[0] => 21
[1] => 25
[2] => 77
[3] => 89
[4] => 98
[5] => 100
)
*/
```

Take note that the inner loop starts from i.

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