PHP explode in array

Question

I was wondering is it possible to convert the following array:

Array (
    "2016-03-03 19:17:59",
    "2016-03-03 19:20:54",
    "2016-05-03 19:12:37"
)

Into this:

Array (
    "2016-03-03",
    "2016-03-03",
    "2016-05-03"
)

Without creating any loops?

Gonna ask the obvious question. What's wrong with loops....? — Jonnix, Oct 09 '16 at 21:56
*"Without creating any loops?"* **NO.** At the end you need to change each array element so you have to loop over the array. Just search how to convert one date format into another and how to apply a function to each array element. — Rizier123, Oct 09 '16 at 21:56
an odd number of questions ask: how to do X without (insert basic php\programming term\function here) — , Oct 09 '16 at 22:01
@nogad there is a simple explanation: they have read somewhere that "loops are slow in php". — zerkms, Oct 09 '16 at 22:01
There's even a simpler explanation (Occam's Razor anyone?)... the homework says "do not use loops" :D — pid, Oct 09 '16 at 22:03
why set homework that has no basis in reality? oh right i remember school now :-) — , Oct 09 '16 at 22:04
i expect the OP not to care but benchmarking of 10 million iterations gives an average of 23 seconds for foreach() vs array_map of 30 seconds — , Oct 09 '16 at 22:21
http://ideone.com/KzmfKd =23 seconds. http://ideone.com/RVGgTm =30 seconds — , Oct 09 '16 at 22:27

Praveen Kumar Purushothaman · Accepted Answer · 2016-10-09T22:20:55.203

9

There's no explicit loops, if you can use array_map, although internally it loops:

function format_date($val) {
  $v = explode(" ", $val);
  return $v[0];
}
$arr = array_map("format_date", $arr);

From the PHP Manual:

array_map() returns an array containing all the elements of array1 after applying the callback function to each one. The number of parameters that the callback function accepts should match the number of arrays passed to the array_map().

Also, when you are dealing with Dates, the right way to do is as follows:

return date("Y-m-d", strtotime($val));

The simple way, using loops is to use a foreach():

foreach($arr as $key => $date)
  $arr[$key] = date("Y-m-d", strtotime($date));

This is the most simplest looping way I can think of considering the index to be anything.

Input:

<?php
$arr = array(
    "2016-03-03 19:17:59",
    "2016-03-03 19:20:54",
    "2016-05-03 19:12:37"
);
function format_date($val) {
  $v = explode(" ", $val);
  return $v[0];
}
$arr = array_map("format_date", $arr);

print_r($arr);

Output

Array
(
    [0] => 2016-03-03
    [1] => 2016-03-03
    [2] => 2016-05-03
)

Demo: http://ideone.com/r9AyYV

edited Oct 09 '16 at 22:20

answered Oct 09 '16 at 21:57

Praveen Kumar Purushothaman

164,888
24
203
252

Hm, a call to `explode()` with only a single argument? – arkascha Oct 09 '16 at 21:59
2

Although this is still loops internally I would expect, I suppose as long as OP can't see them they won't mind :P – Jonnix Oct 09 '16 at 22:00
some one benchmark this against a foreach loop and explode – Oct 09 '16 at 22:08
Thanks a lot! This is much better and faster solution than looping through the entire array. – Beqa Oct 09 '16 at 22:11
"Faster solution". Probably, but I doubt by much ;) – Jonnix Oct 09 '16 at 22:12
@JonStirling The difference between `array_map` and `foreach` will be negligible and since this looks like an academic one, I don't think there'll be much problem. What say? – Praveen Kumar Purushothaman Oct 09 '16 at 22:13
@Beqa it DOES loop the array, just because you dont see it, doesn't mean it doesn't happen – Oct 09 '16 at 22:14
@PraveenKumar Agreed. Just don't want OP to be under their apparent preconception that OMG loops are bad. – Jonnix Oct 09 '16 at 22:14
@nogad I added that in my answer mate. – Praveen Kumar Purushothaman Oct 09 '16 at 22:15
@JonStirling Sure, but I also added the info in the first line. – Praveen Kumar Purushothaman Oct 09 '16 at 22:15
suer but the OP does not seem to get it – Oct 09 '16 at 22:15
1

@PraveenKumar I didn't downvote, but your first answer revision was a very poor one. What I think you can improve is: 1) Explain that `array_map()` also loops through the array 2) Maybe also show how to properly convert one date format into another instead of that "hack" for this specific format. 3) Explain what exactly does `array_map()`. – Rizier123 Oct 09 '16 at 22:15
@Rizier123 yea, sure... I will update them now... Will be helpful for future users... – Praveen Kumar Purushothaman Oct 09 '16 at 22:16
@Rizier123 Check it out.. How does that look? – Praveen Kumar Purushothaman Oct 09 '16 at 22:18
It looks like a mess guys, when some of you make a really useless comments.. If anyone has a better solution, please post it, even if it's done by loops. – Beqa Oct 09 '16 at 22:18
Looks better. (@Beqa Since you have to do something to *every* array element you won't get around with looping through the array, as already explained to you, if you now write the loop your own or just call a function. And probably more times than you think is a simple foreach loop the fastest, since it doesn't have the overhead from a function call.) – Rizier123 Oct 09 '16 at 22:21
@Beqa no its not, i just benchmarked it, array_map vs foreach() is slower (10million iterations, 23 seconds vs 30) – Oct 09 '16 at 22:22
@Beqa Added a minimal `foreach` solution as well. – Praveen Kumar Purushothaman Oct 09 '16 at 22:23
@nogad Great. Thanks. Better than what? – Praveen Kumar Purushothaman Oct 09 '16 at 22:24

score 2 · Answer 2 · edited Oct 11 '16 at 23:22

2

Yes, use map:

function first10($s) {
    return substr($s, 0, 10);
}

$result = array_map("first10", $yourArray);

WARNING: this is a good solution only if you are sure that the date format does not change, in other words the first 10 characters must contain the date.

edited Oct 11 '16 at 23:22

Praveen Kumar Purushothaman

164,888
24
203
252

answered Oct 09 '16 at 21:57

pid

11,472
6
34
63

1

@PraveenKumar validation is not the subject of a question – zerkms Oct 09 '16 at 22:00
1

@PraveenKumar Thanks, I added a warning so he knows where the limits of this solution are. – pid Oct 09 '16 at 22:01

score 1 · Answer 3 · edited May 23 '17 at 12:06

Praveen Kumar's answer is probably the better solution but there is a way to do with what wouldn't really been seen as a loop. instead you use recursion

function explodeNoLoop($array,$delim,$index=0)
{
    $returnArr = array();
    if(isset($array[$index]))
    {
        $expldoed = explode($delim,$array[$index]);
        array_push($returnArr,$expldoed[0]);
    }
    if(isset($array[$index+1]))
    {
        $returnArr = array_merge($returnArr,explodeNoLoop($array,$delim,$index+1));
    }
    return $returnArr;
}

$myArr = array (
    "2016-03-03 19:17:59",
    "2016-03-03 19:20:54",
    "2016-05-03 19:12:37"
);

var_dump(explodeNoLoop($myArr," "));

example

How this code works is that with the function we explode the array at the index provided by the function parameter and add this to our returning array. Then we check if there is a value set at the next index which is +1 of the index we passed into the function. If it exists then we call the function again with the new index with the same array and delimiter. We then merge the results of this with our returner array and then return that.

However, with this one should be careful of nest level errors where you excursively call a function too many times, like looking into the reflection of a mirror in a mirror.

Woooooaaah!!! Wow! But recursion seems to be an overkill for the current situation. LoL. We are thinking creatively. — Praveen Kumar Purushothaman, Oct 09 '16 at 22:23

PHP explode in array

3 Answers3

Linked

Related