arraymap vs foreach loop when creating a comma delimited string

Question

I'm creating a comma delimited string for an SQL query. I would like to know what is better arraymap or a foreach loop. Here are my two examples:

$group_ids = "";
foreach ($group_array as $group_id) {
    $group_ids .= $group_id . ",";
}
$group_ids = rtrim($group_ids, ',');

vs

$group_ids = "";
array_map(function ($group_id) use ($group_ids) {
    $group_ids .= $group_id . ",";
    return;
}, $group_array);
$group_ids = rtrim($group_ids, ',');

Or is there a better way? Or is there literally not much difference?

Using a prepared statement placeholders (rtrim(str_repeat('?,', count($group_array)), ',')) and then executing the query with $group_array as an array of arguments for binding is even better — Mark Baker
– Mark Baker, Commented Oct 3, 2017 at 16:15
array_map() should not be called if you are not going to use its return value. If you want a functional iterator, but do not intend to use the return value, use array_walk(). — mickmackusa
– mickmackusa ♦, Commented Apr 25, 2024 at 4:23

Ralph Thomas Hopper · Accepted Answer · 2017-10-03 16:05:40Z

4

$array = array('lastname', 'email', 'phone');
$comma_separated = implode(",", $array);

from http://php.net/manual/en/function.implode.php

would be more efficient

answered Oct 3, 2017 at 16:05

Ralph Thomas Hopper

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4 Comments

ProEvilz Over a year ago

But is it more efficient?

Daren Chandisingh Over a year ago

In terms of the code, it's easier to follow. Why overcomplicate things? In terms of performance, any difference will be measured in microseconds I expect.

Ralph Thomas Hopper Over a year ago

from what i can gather across the interblargs, implode would be the winner by at LEAST 1ms, if you need to arraymap to clean your data, then use array_walk and get on with your life @Sed

axiac Over a year ago

@ProEvilz From the theoretical point of view, it is much more efficient. It's only one C function call vs. a lot of interpreted code (the foreach version) or, even worse, a lot of PHP function calls (the array_map() version). Even more, implode() internally generates only one string of the final size and copies into it the values of the array. The other versions do a lot of string allocations, copying and deallocations. From the practical point of view, if the array doesn't contain thousands of items, the difference is negligible. But the code is much cleaner using implode().

user8711291 · Accepted Answer · 2017-10-03 16:07:46Z

3

You can also use implode(',',$array_of_ids). Just make sure you trim your values before using the implode.

$ids = ['foo','bar','boo'];
$ids = array_map('trim',$ids);
$ids_list = implode(',',$ids);
echo $ids_list; # foo,bar,boo

answered Oct 3, 2017 at 16:07

user8711291

1 Comment

axiac Over a year ago

While the call to trim() is useful to produce a nice string, it doesn't add any value in this context. If the string generated this way is used to construct a IN (...) fragment of an SQL query, the whitespace do not matter. But with or without trim(), the answer is correct, nevertheless.

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