有人可以解释内部的PHP数组排序代码如何工作？

Question

I have some problems with PHP right now. I don't know how to create a code which sorts numbers in array from lowest to highest (and contrariwise). I'm only allowed to use loops and conditions without using PHP built-in functions, so I can understand how these functions work.

I found this code on Stack overflow sorting array value without using built in php like sort() etc:

<?php

$array=array('2','4','8','5','1','7','6','9','10','3');

echo "Unsorted array is: ";
echo "<br />";
print_r($array);


for($j = 0; $j < count($array); $j ++) {
    for($i = 0; $i < count($array)-1; $i ++){

        if($array[$i] > $array[$i+1]) {
            $temp = $array[$i+1];
            $array[$i+1]=$array[$i];
            $array[$i]=$temp;
        }       
    }
}

echo "Sorted Array is: ";
echo "<br />";
print_r($array);

?>

Can someone please explain step by step on each line how part of the code below works? I lose concentration when trying to understand this.

for($j = 0; $j < count($array); $j ++) {
        for($i = 0; $i < count($array)-1; $i ++){

            if($array[$i] > $array[$i+1]) {
                $temp = $array[$i+1];
                $array[$i+1]=$array[$i];
                $array[$i]=$temp;
            }       
        }
    } 

Answer 1

Just relax. :) This is one of the easiest code.

In your code:

<?php

$array=array('2','4','8','5','1','7','6','9','10','3');

//array declared with members

echo "Unsorted array is: ";
echo "<br />";
print_r($array);

//will output the present condition of your array

for($j = 0; $j < count($array); $j ++) {

//this is the first for loop. here, count($array) will return 10 as you have 10 members inside your array. So simply it just for($j = 0; $j < 10; $j ++). This for will loop through 0-9.

for($i = 0; $i < count($array)-1; $i ++){

//this is the second for loop. here, count($array)-1 will return 9. So simply it just for($i = 0; $i < 9; $i ++). This for will loop through 0-8.

    if($array[$i] > $array[$i+1]) {
            $temp = $array[$i+1];
            $array[$i+1]=$array[$i];
            $array[$i]=$temp;
        }       
    }
}

//this is the main part of your code. It check if a array member is greater than it's next member. If so then it swap the position or the code continue as there is no "else" statement. Suppose value of i is 0. Then if($array[0] > $array[1])->if(2>4) answer is no, so the code continue. Suppose value of i is 2. Then if($array[2] > $array[3])->if(8>5) answer is yes, now just swapping position happen. $temp=5 then $array[3]=$array[2] then $array[2]=5.

echo "Sorted Array is: ";
echo "<br />";
print_r($array);

?>

//just print the sorted array.