Delete element from array if not found

Question

I have some code I created which is supposed to see if something exists in an array of strings. If it does not exist, I want to delete that element of the array. I thought we do this with unset, but it doesnt seem to be working. Mind helping?

echo '<br>size of $games before end-check: '.sizeof($games);
foreach ($games as $game) {
    $game_end_marker = "body = (game)#";
    $game_end_pos = strpos($game, $game_end_marker);
    if ($game_end_pos !== false) {
        echo "<br>end of game found";
    } 
    else {
        echo "<br>end of game not found. incomplete game";
        unset($game);
    }
}
echo '<br>size of $games after end-check: '.sizeof($games);

output:

size of $games before end-check: 2  
end of game found  
end of game not found. incomplete game  
size of $games after end-check: 2

you should unset from $games not $game, $game is temporary created by the foreach function. — , Dec 21 '11 at 18:51
Refer this answer: [How to delete an element from an array in php?](http://stackoverflow.com/a/369761/500725) — Siva Charan, Dec 21 '11 at 18:56

score 4 · Accepted Answer · answered Dec 21 '11 at 18:50

Because you unset the variable $game, not the element in the array. Try this:

echo '<br>size of $games before end-check: '.sizeof($games);
foreach ($games as $index => $game) {
    $game_end_marker = "body = (game)#";
    $game_end_pos = strpos($game, $game_end_marker);
    if ($game_end_pos !== false) {
        echo "<br>end of game found";
    } 
    else {
        echo "<br>end of game not found. incomplete game";
        unset($games[$index]);
    }
}
echo '<br>size of $games after end-check: '.sizeof($games);

This did the trick, and I learned how to do this now with $key => $value in a foreach loop. Thanks! — pr0tocol, Dec 21 '11 at 19:05

score 2 · Answer 2 · answered Dec 21 '11 at 18:50

2

You have to unset the index of game.

foreach ($games as $key => $value) {
  // all your logic here, performed on $value
  unset($games[$key]);
}

answered Dec 21 '11 at 18:50

dm03514

54,664
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score 2 · Answer 3 · answered Dec 21 '11 at 18:51

2

This merely unsets your local reference to the element. You need to be referring directly to the array.

foreach($games as $key => $game)
    unset($games[$key]);

answered Dec 21 '11 at 18:51

Alex Turpin

46,743
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I marked an identical solution above, but yes - this is the correct answer! Thank you – pr0tocol Dec 21 '11 at 19:08
@pr0tocol his was a more complete solution. Glad I could help. – Alex Turpin Dec 21 '11 at 19:15
Yes, but don't want to take anything away from you. I appreciate the time – pr0tocol Dec 21 '11 at 19:21

score 0 · Answer 4 · answered Dec 21 '11 at 18:53

That won't work: foreach creates a new variable, copying the old one. Unsetting it will do nothing to the original value. Likewise, making it a reference won't work either, since only the reference would be deleted.

The nicest way to do this would be with array_filter:

$games = array_filter($games, function($game) {
    $game_end_marker = "body = (game)#";
    $game_end_pos = strpos($game, $game_end_marker);

    if ($game_end_pos !== false) {
        echo "<br>end of game found";
        return true;
    } 
    else {
        echo "<br>end of game not found. incomplete game";
        return false;
    }
});

This uses the anonymous function syntax introduced in PHP 5.3. If the function returns true, the element is kept; if it returns false, the element is removed.

I marked the answer above, and this is incorrect per the implemented solution results. Using `foreach ($games as $index => $game)`, I was able to do `unset($games[$index])` and it persisted outside of the foreach loop. — pr0tocol, Dec 21 '11 at 19:08

score 0 · Answer 5 · answered Dec 21 '11 at 18:55

0

You can also call by reference:

foreach($games as &$game) {
    unset($game);
}

In this way you can also change $game (eg. $game .= " blah";) and the original array will be modified.

answered Dec 21 '11 at 18:55

Niet the Dark Absol

320,036
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464
592

1

No, that will have no effect. Calling `unset` on a reference will only delete the reference, not the original value. – lonesomeday Dec 21 '11 at 18:57
Ah, fair enough. But the reference thing still applies for the changing values, so I'll leave that in case it's useful to the asker. – Niet the Dark Absol Dec 21 '11 at 21:21

score 0 · Answer 6 · answered Dec 21 '11 at 18:58

You can use array_splice in conjunction with an incrementally-increasing index variable to remove the current item from the array:

$index = 0;
foreach ($games as $game) {
    $game_end_marker = "body = (game)#";
    $game_end_pos = strpos($game, $game_end_marker);
    if ($game_end_pos !== false) {
        echo "<br>end of game found";
    } 
    else {
        echo "<br>end of game not found. incomplete game";
        array_splice($games, $index, 1);
    }
$index++;
}

Delete element from array if not found

6 Answers6