Using next in foreach loop

Question

I am looping through an array using foreach.

In a particular situation I need to know the value of the next element before iteration comes to that(like a prediction) element. For that I am planning to use the function next().

In documentation I just noticed that next() advances the internal array pointer forward.

next() behaves like current(), with one difference. It advances the internal array pointer one place forward before returning the element value. That means it returns the next array value and advances the internal array pointer by one.

If so will it affect my foreach loop?

@Jonas while you are editing all of these tags are you considering the possibility of closing duplicates? I think I've seen some dupe closure candidates in your page stirring wake. — mickmackusa
– mickmackusa ♦, Commented May 12, 2023 at 12:17

Shawn Mehan · Accepted Answer · 2015-12-10 05:53:54Z

10

It will not affect your loop if you use it in this way

<?php

$lists = range('a', 'f');

foreach($lists as &$value) {
   $next = current($lists);
   echo 'value: ' . $value . "\n" . 'next: ' . $next . "\n\n";
}

OUTPUT

value: a next: b

value: b next: c

value: c next: d

value: d next: e

value: e next: f

value: f next:

edited Dec 10, 2015 at 5:53

Shawn Mehan

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answered Jul 31, 2013 at 6:10

liyakat

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4 Comments

e-motiv Over a year ago

Awesome find. I hope it is stable and forward_compatible. And yes it can be useful. :-)

Warren Over a year ago

Should the line $next = current($lists); be $next = next($lists);?

liyakat Over a year ago

No it's not, you can run this code to your local php environment and try

flu Over a year ago

@e-motiv This is not stable and forward-compatible. It isn't even backward-compatible. As tested with sandbox.onlinephpfunctions.com this always states "a" as being next in PHP 5.0.4 to 5.1.6. Then from 5.2.16 to 5.6.29 its "b", "c", "d", "e", "f" (so your output) and from 7.0.1 onwards it stays "a". As pointed out in grokbase.com/t/php/php-internals/13bjdgjhcz/… foreach and current have nothing to do with each other.

mlncn · Accepted Answer · 2019-09-18 16:48:30Z

4

next() doesn't affect foreach(), period.

In PHP 7.2 at least,

$values = ['a', 'b', 'c', 'd', 'e'];

foreach ($values as $value) {
  next($values);
  $two_ahead = next($values);
  echo("Two ahead: $two_ahead\n");
  echo("Current value: $value\n");
}

Produces:

Two ahead: c
Current value: a
Two ahead: e
Current value: b
Two ahead: 
Current value: c
Two ahead: 
Current value: d
Two ahead: 
Current value: e

Also note that the foreach loop does not affect the position of next, either. They're independent.

If you have an array with sequential numeric keys (the default), then ops' answer is best for what you're trying to do. I merely answered the question.

answered Sep 18, 2019 at 16:48

mlncn

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Comments

ops · Accepted Answer · 2013-07-31 06:10:10Z

1

Try this code:

$a=$array();
foreach($a as $key=>$var)
{
   if(isset($a[$key+1]))
      echo $a[$key+1];//next element
}

answered Jul 31, 2013 at 6:10

ops

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1 Comment

Dan Over a year ago

This assumes integer indexed array with contiguous keys, which of course arrays in PHP need not be either. If you wish to safely use this method with unknown arrays or non-integer keys then iterate the result of array_values($a).

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