Nested Loop PHP

Question

i have code :

<?php
$number =9;
$number2 = $number / 2;
    for ($b=0; $b<=$number2; $b++){
        for ($i=$number; $i>=1; $i--){
            echo $i;
        }
        echo "<br/>";
        for ($a=1; $a<=$number; $a++)
        {
        echo $a;
    }
    echo "<br/>";
}
?>

I want the result like this .

why if i put odd number like 9 , why always the result 10 loop ?

Because loop is starting from 0 so total iterations 0,1,2,3,4 that's 5 times and you have two inner loops so 5*2 = 10 loop — DEarTh
– DEarTh, Commented May 5, 2018 at 17:26

Gabriel · Accepted Answer · 2018-05-05 17:45:18Z

3

You have two loops in a loop, therefore you'll always get an even number of lines.

You don't actually need that structure, see:

$number=9;
$k=0;
$sum=1;
for($i=1; $i<=$number; $i++) {
    for($j=1; $j<=$number; $j++) {
        $k+=$sum;
        echo $k;
    }
    echo '<br>';
    //Sum once again so in the next iteration $k is 0 or 10
    $k+=$sum;
    //Invert the sign of $sum so in the next iteration it substracts, and then adds, and so on
    $sum*=-1;
}

Also note that going from 0 to $number inclusive (lower or equal comparation) you'll get one iteration more (from 0 to 9 there are 10 whole numbers).

edited May 5, 2018 at 17:45

answered May 5, 2018 at 17:39

Gabriel

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3 Comments

M. Eriksson Over a year ago

@ZakarioLesrahmanto - If it worked for you, you should accept the answer so other users know it's been solved.

Zakario Lesrahmanto Over a year ago

Hi magnus , the result its start 123456789 . i want first row is 987654321 , how i get it ?

Gabriel Over a year ago

Start from $k=10 and $sum=-1. Analyze the code, it's really simple!

Zakario Lesrahmanto · Accepted Answer · 2018-05-05 19:36:37Z

0

Solve with this code , thx Gabriel.

$number=9;
$k=0;
$sum=1;
for($i=1; $i<=$number; $i++) {
    for($j=1; $j<=$number; $j++) {
        $k+=$sum;
        echo $k;
    }
    echo '<br>';
    //Sum once again so in the next iteration $k is 0 or 10
    $k+=$sum;
    //Invert the sign of $sum so in the next iteration it substracts, and then adds, and so on
    $sum*=-1;
}

edited May 5, 2018 at 19:36

answered May 5, 2018 at 18:43

Zakario Lesrahmanto

679 bronze badges

4 Comments

M. Eriksson Over a year ago

I didn't do anything to help you. It was all Gabriel. And I must say that it's quite disrespectful towards Gabriel (who was nice enough to spend his time helping you) to post his answer as your own instead of accepting his.

M. Eriksson Over a year ago

Actually, I see that you haven't accepted one single answer on any of your questions, though you got plenty of answers. That's very disrespectful. If people take their time helping you, you could at least recognize it.

Zakario Lesrahmanto Over a year ago

i'm sorry for not concentrating, in here it so late night , now in my country is 3AM . T_T

M. Eriksson Over a year ago

...and still you haven't accepted Gabriels answer. =/

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