Modify next element in array during foreach() loop

Question

How can I modify the next element in a foreach() loop, during the loop? I think it has something to do with talking to the variable by reference but I'm not sure how. i.e.:

$arr = array( array('color' => 'red',    'type' => 'apple'),
              array('color' => 'yellow', 'type' => 'banana'),
              array('color' => 'purple', 'type' => 'grape')
            );

foreach($arr as $k => $v) {
   echo "<br> The ".$v['type'].' fruit is '.$v['color'];

   // change the color of the next fruit?
   if($v['type'] == 'apple') { $arr[$k+1]['color'] = 'green'; }
}

I'd like this to tell me the banana is green, but it stubbornly sticks to the banana being yellow...

(UPDATE: fixed a stupid logic error in my original question. The answer marked below is correct.)

ncremins · Accepted Answer · 2012-02-28 00:59:33Z

5

foreach loops through an array by taking a copy of the array and not by reference. You need to loop through the array by reference using the ampersand & on the array value.

foreach($arr as $k => &$v) {
   echo "<br> The ".$v['type'].' fruit is '.$v['color'];

   // change the color of the next fruit?
   if($v['type'] == 'banana') { $arr[$k+1]['color'] = 'green'; }
}

answered Feb 28, 2012 at 0:59

ncremins

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4 Comments

Felix Kling Over a year ago

That's only one part of the solution (but nevertheless very important one). When $v['type'] == 'banana' is true, the next fruit which is modified is grape. If the banana should be green it must be $v['type'] == 'apple'.

ncremins Over a year ago

I misread, I assumed when the original poster was refering to the next element he meant to change the color of the grape to green.

Felix Kling Over a year ago

Well, I don't know. Using the reference solves the programming error. But he also stated I'd like this to tell me the banana is green, in which case he also has a logic error. But your answer should get him to the right track.

Eric Over a year ago

Oops, my bad on the logic (I wrote that script quickly here on StackOverflow without actually testing it)... but you understood what I was after and your answer is working for me, so... thanks!

Mike Purcell · Accepted Answer · 2012-02-28 01:05:58Z

0

$k=array_keys($yourarray);
    for($i=0; $i<sizeof ($k); $i++) {
       if($yourarray[$k[$i]] == "something") {
           $yourarray[$k[$i+1]] = "something else"; 
       }
    }
}

sorry formatting is all wonky as i am replying from a phone...

edited Feb 28, 2012 at 1:05

Mike Purcell

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answered Feb 28, 2012 at 1:03

iWantSimpleLife

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Comments

Stephen Senkomago Musoke · Accepted Answer · 2012-02-28 04:17:43Z

-1

The counter has to remain the same

$arr = array( array('color' => 'red',    'type' => 'apple'),
          array('color' => 'yellow', 'type' => 'banana'),
          array('color' => 'purple', 'type' => 'grape')
        );

foreach($arr as $k => $v) {
  echo "<br> The ".$v['type'].' fruit is '.$v['color'];

  // change the color of the next fruit?
  if($v['type'] == 'banana') { $arr[$k]['color'] = 'green'; }

  // now echo the new color from the original array 
   echo "<br> The ".$arr[$k]['type'].' fruit is now '.$arr[$k]['color'];
}

answered Feb 28, 2012 at 4:17

Stephen Senkomago Musoke

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