Counting the value when calling a function

Question

I need some help as I am new on this. I am working on a function to add the day value that start from 0 to 6. I want to count it up the value for each day so I can connect to each url for each day, but on my code it will only show the value as 0 for each day.

Here is the code:

<?php

$channels = json_decode(file_get_contents('channels.json'), true);
$day = 0;

function get_shows($channel_id, DateTime $dt, $duration=1440, $skip_finished = true) 
{
    $url = 'http://example.comapi/GS?cid=' . $channel_id . '&offset=+00.00&day=' .$day++;
    echo $url;
    $day++;
}


if(!isset($_GET['id']) || !isset($channels[$_GET['id']])) 
{
    //some random code.....
}
else
{
    // today + 6 following days
   for($day=0; $day<=6; $day++) 
   {
      // display date      
      echo '<h3>', $dt->format('Y-m-d (l)'), '</h3>';

      // display shows
      foreach(get_shows($channel_id, $dt, $duration) as $show) 
      {

      }
      $dt->add(new DateInterval('P1D'));
      $dt->setTime(0, 0, 0);
    }
}
?>

Output:

2018-05-04 (Friday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=0

2018-05-05 (Saturday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=0

2018-05-06 (Sunday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=0

2018-05-07 (Monday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=0

2018-05-08 (Tuesday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=0

2018-05-09 (Wednesday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=0

2018-05-10 (Thursday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=0

Here is what I want to achieve:

2018-05-04 (Friday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=0

2018-05-05 (Saturday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=1

2018-05-06 (Sunday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=2

2018-05-07 (Monday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=3

2018-05-08 (Tuesday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=4

2018-05-09 (Wednesday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=5

2018-05-10 (Thursday)
http://example.com/api/GS?cid=44630&offset=+00.00&day=6

Can you please show me an example how I can add up the value for each day that start from 0 to 6 when I am calling on a function??

`global $day` inside get_show will help immensely. Also you're incrementing $day twice in the method when obviously you should only do it once. — vogomatix, May 04 '18 at 15:03
thank you, can you please post the answer of what I should use so I would mark this as the answer? — Robert Jones, May 04 '18 at 15:04

score 1 · Accepted Answer · answered May 04 '18 at 15:05

1

Inside a function, variables only have local scope unless you explicitly say otherwise.

$day = 0;

function get_shows($channel_id, DateTime $dt, $duration=1440, $skip_finished = true) 
{
    global $day;
    $url = 'http://example.comapi/GS?cid=' . $channel_id . '&offset=+00.00&day=' .$day++;
     echo $url;
     // don't need this either as you've already post incremented $day
     // $day++;
 }

As others have stated, using global variables is not a good technique and you should really be passing $day into the method.

answered May 04 '18 at 15:05

vogomatix

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oh thank you very much for this as it is working great. Problem are now solved! – Robert Jones May 04 '18 at 15:11
No problem, but look at the other answers as whilst my answer fixes your problem, the other answers are better programming solutions – vogomatix May 05 '18 at 10:52

score 0 · Answer 2 · answered May 04 '18 at 15:05

Either use the global that exist by adding global $day in your function:

function get_shows($channel_id, DateTime $dt, $duration=1440, $skip_finished = true) 
{
    global $day;
    $url = 'http://example.comapi/GS?cid='.$channel_id.'&offset=+00.00&day='.$day;
    echo $url;
}

Also remove the increments to $day as they are not needed, your already did this in your loop. Or add an extra parameter and pass $day into your function and use that:

get_shows($channel_id, DateTime $dt, $day, $duration=1440, $skip_finished = true)

score 0 · Answer 3 · answered May 04 '18 at 15:06

Pass $day into the function as a parameter. You're already looping over it but not using it. Your other option is to declare the variable as global, or static within the function body, both of which are not sensible choices.

Change

function get_shows($channel_id, DateTime $dt, $duration=1440, $skip_finished = true)

to

function get_shows($channel_id, DateTime $dt, $day, $duration=1440, $skip_finished = true);

and call it using

get_shows($channel_id, $dt, $day, $duration)

You don't need to increment the variable within the function as well as the loop - let the function do one thing, based on the parameters passed to it.

score 0 · Answer 4 · answered May 04 '18 at 15:09

The answer is: scope!

You are trying to access a variable that exists outside the function, which does not work in PHP. Each time you call $day++, $day does not exist, so PHP will try to initialize it with the value 0. That's why every url has day=0 in it.

using the "global" keyword is not recommended, because it will eventually lead to very messy code, which can be hard to debug.

I'd recommend something like this (simplified version):

function getShowUrl($channel_id, $day) 
{
    return 'http://example.comapi/GS?cid=' . $channel_id . '&offset=+00.00&day=' .$day;
}

for($day = 0; $day < 7; $day++) {
    echo getShowUrl($channel_id,$day);
}

Using echo inside a function is usually not recommended. Using return enables you to reuse the function for another implementation.

Counting the value when calling a function

4 Answers4