Adding to an array while 'it'-erating, or, is 'Oleg' Swedish for 'recurse' ...

dalecosp

Is anyone already aware of how to push an element/value onto an array, while inside an iterating loop using that array, and still be able to use that element/value in the loop?

I wasn't until today. Very grateful to "Oleg" who, in the PHP manual comments for [man]foreach/man, pointed this out (I was in a foreach() loop and had tried both array_push() and bracket notation to no avail:

$array = range(1,10);

while (list($arr,$val) = each( $array )) {

   if ($val == 5) {
      $array[] = 11;
   }
   echo $val.PHP_EOL;
}

So, if your Real Name(tm) is "Oleg" and you wrote that comment, thank you very much!

(Are there any other ways to do this?)

Weedpacket

Ooo...kay.... I can see that. That is quite neat. It's basically the PHP analogue of SQL's Recursive Common Table Expressions. Or maybe it's the other way around, since I think PHP's array iteration constructs predate the SQL standard.

You could do it with foreach with a temp array to store additional work and an outer loop that checks to see if there is any:

$array = range(1,10);
do
{
	$more = [];
	foreach($array as $val) {
		if($val == 5)
		{
			$more[] = 11;
		}
		echo $val,PHP_EOL;
	}
	$array = $more;
} while(!empty($more));

The behaviour is different outside the loop(s) though: the final result there is an empty [font=monospace]$array[/font] while Oleg's leaves it with every element it started with and every element added to it.

Incidentally, the Code Share thread could do with a little love🙂

dalecosp

Weedpacket;11047005 wrote:
You could do it with foreach with a temp array to store additional work and an outer loop that checks to see if there is any:
...

The behaviour is different outside the loop(s) though: the final result there is an empty $array while Oleg's leaves it with every element it started with and every element added to it.

Leave it to the genius ... it certainly didn't occur to me. I needed the array to remain, so Oleg's is a little better, but you're quite one with the machine, as always. ;-)

Incidentally, the Code Share thread could do with a little love🙂

Ah, I suppose so; it's Oleg's, too bad he won't put it there?

Most of "my" code is probably too ugly or too secret to share. 😛

I'll think about it; but I thought maybe some Google-love might come of me sharing it someplace with a good rep like ... PHPBuilder?

Derokorian

Couldn't you just do a for loop using count?

$a = array(1,2,3);
for($i=0; $i<count($a);$i++) {
   $b = $a[$i];
   if ($b < 3) {
      $a[] = $b*3;
   }
   echo "$b\n";
}

Output:

1
2
3
3
6

dalecosp

I suppose you could, as long as the indices were ordered ints?

I think Oleg's code would handle an array without caring what the keys were, per se ... I'll test. :-)

dalecosp

Hmm: it would need to be modified a bit for an associative array; perhaps that's obvious to you.

Don't try this on the production box:

<?php

$a = array("blah"=>1,"blargh"=>2,"blip"=>3);

for($i=0; $i<count($a);$i++) {
   $b = $a[$i];
   if ($b < 3) {
      $a[] = $b*3;
   }
   echo "$b\n";
}

Derokorian

Ok, fixed for associative 🙂

$a = array("blah"=>1,"blargh"=>2,"blip"=>3);

for($i=0; $i<count($a);$i++) {
   $b = current(array_slice($a, $i, 1));
   if ($b < 3) {
      $a[] = $b*3;
   }
   echo "$b\n";
}

Derokorian

And just for shiggles, with keys:

$a = array("blah"=>1,"blargh"=>2,"blip"=>3);

for($i=0; $i<count($a);$i++) {
   $e = array_slice($a, $i, 1);
   $k = key($e);
   $v = current($e);

   if ($v < 3) {
      $a["triple_$k"] = $v*3;
   }
   echo "$k => $v\n";
}

Weedpacket

dalecosp;11047039 wrote:
Ah, I suppose so; it's Oleg's, too bad he won't put it there?

Well, some of the algorithms I've put there didn't originate with me (Roman numerals, fast set intersection) either - I just did the implementation.

Weedpacket

Huh. From [man]each[/man]:

Warning: This function has been DEPRECATED as of PHP 7.2.0. Relying on this function is highly discouraged.

Which means it will be gone by PHP 8.

NogDog

Weedpacket;11062939 wrote:
Huh. From [man]each[/man]:

Which means it will be gone by PHP 8.

That seems...weird. Why break long-standing code by getting rid of that function -- just because it's undefined what it will do with an object? 🙁 (Mind you, I think I could count on one had the times of used it, but...shrug.)

Weedpacket

https://wiki.php.net/rfc/deprecations_php_7_2#each

NogDog

Weedpacket;11062953 wrote:
https://wiki.php.net/rfc/deprecations_php_7_2#each

Looks like "bishop" is against deprecating anything. 🙂

dalecosp

NogDog;11062955 wrote:
Looks like "bishop" is against deprecating anything. 🙂

Wonder what PHP would look like, to the tech-world-at-large, if they only did things that were unanimous (or nearly so). 18 to 6 is a 75% "mandate", for sure, but it's hardly unanimous like most of the other changes listed there.

A lot of the general criticism of the language actually seems, to me, to stem from the populist approach taken by the developers. By the same token, it could be that "holdouts" like the six who voted against the deprecation of each() are the cause of some of the foibles ... (we could probably talk a LONG time about this idea...)

dalecosp

Looks like a couple of these might bite me:

quote=wiki.php.net cast
parse_str() without second argument[/quote]I've got unset() all over the place in some large production systems ...

Of course, to be fair to me, so does PHPExcel, vBulletin, SimpleDOM, PHPMyAdmin ... 😉

NogDog

dalecosp;11062959 wrote:
Looks like a couple of these might bite me:

I've got unset() all over the place in some large production systems ...

Of course, to be fair to me, so does PHPExcel, vBulletin, SimpleDOM, PHPMyAdmin ... 😉

I don't think unset() would be deprecated, but some usage where you can cast something to unset -- which sounds weird/confusing to me anyway. 🙂

dalecosp

NogDog;11062961 wrote:
I don't think unset() would be deprecated, but some usage where you can cast something to unset -- which sounds weird/confusing to me anyway. 🙂

Ah ... that makes a tad more sense.