PHP: Loop Logic

Question

I realize this is extremely simple but I feel I'm over-looking something. What I want to screen to display is

RED This is 0.

or

GREEN This is 1.

And for it to alternate back and forth between the displayed text. My logic if fine for alternating between Red and Green, but the "This is 0" and "This is 1" text is not displaying.

Here is my code so far:

<?php

$array = array(0=>"RED",1=>"GREEN");
$a_count = 0;
$count = 0;


while($count<10)
// DO 9 TIMES
{

    echo $array[$a_count] . ' ';
    //SUDO FOR IMAGE BEING DISPLAYED

    while($array[$a_count] == 0)
    {
        echo "This is 0.<br>";
    }

    while($array[$a_count] == 1)
    {
        echo "This is 1<br>";
    }


//<----SWITCH BACK AND FORTH---->
    if($a_count == 1)
    {
        $a_count = 0;
    }
    else
    {
        $a_count++;
    }
//<----------------------------->
    $count++;
}

?>

I realize the easiest way to get what I would like is:

<?php

$array = array(0=>"RED",1=>"GREEN");
$a_count = 0;
$count = 0;


while($count<10)
// DO 9 TIMES
{

    echo $array[$a_count] . ' ';
    //SUDO FOR IMAGE BEING DISPLAYED


//<----SWITCH BACK AND FORTH---->
    if($a_count == 1)
    {
        echo "This is 1<br>";
        $a_count = 0;
    }
    else
    {
        echo "This is 0.<br>";
        $a_count++;
    }
//<----------------------------->
    $count++;
}

?>

But this code does not contain the logic I need for the continuation of this project. I would greatly appreciate an answer as to why my first code is not printing "This is 0."

Thank you!

What logic r u looking for? You have answered your own question — user2541120
– user2541120, Commented Jul 31, 2013 at 16:47

Community · Accepted Answer · 2017-05-23 12:28:53Z

3

What you are looking for is a mod count.

Change your loop for:

for($i=0;$i<10;$i++){
    echo $array[$i%2].' This is '.($i%2);
}

The modulo operator returns the remainder of a division. See: What are the practical uses of modulus (%) in programming?

edited May 23, 2017 at 12:28

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answered Jul 31, 2013 at 16:51

charlespwd

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Comments

Marc B · Accepted Answer · 2013-07-31 16:48:00Z

1

Why not something like this:

$colors = array(0 => 'Red', 1 => 'Green');
$idx = 0;
$count = 0;
while($count < 10) {
    echo "The color is {$colors['$idx']}<br />";
    $count = 1 - $count; // if $count is 1, it becomes 0. if it's 0, it becomes 1
}

Your while() loops are basically totally useless. You're trying to compare the RED and GREEN strings again 0. If either evaluation happens to be true, you'll end up with an infinite loop.

answered Jul 31, 2013 at 16:48

Marc B

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Comments

Kris · Accepted Answer · 2013-07-31 16:52:05Z

0

Ignoring the inefficiency of this script, your while loops are comparing against the array's values, not its keys. But fixing this problem will actually expose another - an infinite loop.

answered Jul 31, 2013 at 16:52

Kris

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Comments

StephenTG · Accepted Answer · 2013-07-31 16:54:53Z

0

You aren't changing the value of $a_count in your while loops, so there is no way for them to end.

The problem is here:

while($array[$a_count] == 0)
{
    echo "This is 0.<br>";
}

while($array[$a_count] == 1)
{
    echo "This is 1<br>";
}

Once it enters the first loop, it will just keep echoing "This is 0.<br>", as $a_count is unchanging.

It looks like you could change these whiles to ifs to make your code work the way you want. You also probably want to check that $a_count is 0 or 1, rather than $array[$a_count]

edited Jul 31, 2013 at 16:54

answered Jul 31, 2013 at 16:48

StephenTG

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Comments

Yoann Augen · Accepted Answer · 2013-07-31 17:00:30Z

0

Well, in your first example before the while($count<10), have you initilize your values? If you do, you must have a display like that :

RED This is 0.0
This is 0.0
This is 0.0
This is 0.0
This is 0.0
...

"This is 0.0" is display in a infinite loop.

    while($array[$a_count] == 0)
    {
        echo "This is 0.$count<br>";
    }

    while($array[$a_count] == 1)
    {
        echo "This is 1<br>";
    }

You must change the value in a while loop.

Other tips, I think you mush take a look at "foreach" php loop. Can be useful for what you want to do. modulos can also help you.

answered Jul 31, 2013 at 17:00

Yoann Augen

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3 Comments

bee Over a year ago

Unfortunately, that is not what I'm getting This is what I'm getting is: RED GREEN GREEN GREEN GREEN GREEN GREEN GREEN GREEN

bee Over a year ago

I also initialized $count while declaring my variables at the very beginning.

Yoann Augen Over a year ago

Do you have? : $array = array(0=>"RED",1=>"GREEN"); $a_count = 0; $count = 0; I copy/paste your first code, adding this at the begining.

bee · Accepted Answer · 2013-08-01 14:56:49Z

0

I think probably the easiest way to do this is to just use a switch statement. I feel really silly for not thinking of it before.

while($count<10)
{

    echo $array[$a_count] . ' ';
    //PSUEDO FOR IMAGE BEING DISPLAYED

    switch($a_count):
    {
        case 1:
            echo "This is RED.<br>";
            $a_count = 0;
            break;

        case 0:
            echo "This is GREEN.<br>";
            $a_count++;
            break;

    }

    $count++;
}

answered Aug 1, 2013 at 14:56

bee

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