PHP group certain results from foreach on array into another array

Question

I have an array that looks something like this:

$array =  array( [0] => FILE-F01-E1-S01.pdf 
                 [1] => FILE-F01-E1-S02.pdf 
                 [2] => FILE-F01-E1-S03.pdf 
                 [3] => FILE-F01-E1-S04.pdf 
                 [4] => FILE-F01-E1-S05.pdf 
                 [5] => FILE-F02-E1-S01.pdf 
                 [6] => FILE-F02-E1-S02.pdf 
                 [7] => FILE-F02-E1-S03.pdf );

Basically, I need to look at the first file and then get all the other files that have the same beginning ('FILE-F01-E1', for example) and put them into an array. I don't need to do anything with the other ones at this point.

I've been trying to use a foreach loop finding the previous value to do this, but am not having any luck.

Like this:

$previousFile = null;

foreach($array as $file)
{

    if(substr_replace($previousFile, "", -8) == substr_replace($file, "", -8)) 
    {
        $secondArray[] = $file;
     }

    $previousFile = $file;
}

So then $secondArray would look like this:

    Array ( [0] => FILE-F01-E1-S01.pdf [1] => FILE-F01-E1-S02.pdf 
            [2] => FILE-F01-E1-S03.pdf [3] => FILE-F01-E1-S04.pdf 
            [4] => FILE-F01-E1-S05.pdf)

As my result.

Thank you!

Sample code always helps to see where you are so far. Would it be possible to use a simple `foreach()` and `if()`, with a regular expression condition? — HoldOffHunger, Sep 27 '18 at 18:40
First you need to define your pattern. Is it always going to be `FILE-F[NUMBER]-*.pdf` ? What is your use case for the array? Do you just want to get let's say `F01` files array or you want to parse them all at once into their separate arrays? Please provide us with more context. — Jan Richter, Sep 27 '18 at 18:43
@falnyr The files will vary in how they are named. I can't do a strpos() on them because it will differ. I can, however always remove the last 8 characters to match them. And, yes, I do just want an array of F01 files. That's all I need to do at this point. I hope that clears things up a bit. — matty_eng, Sep 27 '18 at 18:51
@matty_eng Are you sure about the last 8 characters? What you are showing here seems to be a list of episodes for a TV show. What if the name would be `E01-S1` can that happen? — Jan Richter, Sep 27 '18 at 18:55
Why are you reassigning `$previousFile` every time through the loop? You said you just want to use the first file to get the pattern. — Barmar, Sep 27 '18 at 19:09

score 1 · Answer 1 · answered Sep 27 '18 at 18:43

1

You can use array_filter combined with strpos:

$result = array_filter($array, function($filename) { 
  return strpos($filename, 'FILE-F01-E1') === 0; 
});

answered Sep 27 '18 at 18:43

Jeto

14,596
2
32
46

Rook · Answer 2 · 2018-09-27T18:53:14.030

0

Run a simple foreach with strpos() which looks for an occurrence of a string within a string.

 $results = array();

 foreach($array as $item){
      if (strpos($item, 'FILE-F01-E1') === 0) {
           array_push($results, $item);
      }
 }

edited Sep 27 '18 at 18:53

answered Sep 27 '18 at 18:43

Rook

141
13

2

I believe your `strpos` test is wrong. First position will return 0 which doesn't evaluate to true. Any other position will evaluate to true (after your edit, with `===` the condition will never be met now :) ) – Jeto Sep 27 '18 at 18:46
Thanks. I believe that I have fixed it! – Rook Sep 27 '18 at 18:50
2

Almost: I believe you meant `=== 0`. You want to add the items which *do* have that string at their first position. – Jeto Sep 27 '18 at 18:51
Ah yes. To be honest, this is not the best use of `strpos()`. I appreciate the corrections! I actually was unaware of the `array_filter()` function! Very handy. – Rook Sep 27 '18 at 18:52
**strpos** returns **FALSE** if the needle was not found. So you should check against **FALSE** with the **===** operator, not **0**. – inquam Sep 27 '18 at 18:55
1

@inquam Thanks for the feedback. However I am only interested in the condition being met if the position of the desired string is at place 0. I don't want to condition to be met if it is indeed false. – Rook Sep 27 '18 at 18:56
@Rook, then it makes perfect sense :) – inquam Sep 27 '18 at 19:07

inquam · Accepted Answer · 2018-09-27T19:06:43.817

Are you sure this will be the naming format? That is crucial information to have to construct a regexp or something to check for being a substring of the following strings.

If we can assume this and that the "base" name is always at index 0 then you could do something like.

<?php
    $myArr =  [ 
                'FILE-F01-E1-S01.pdf', 
                'FILE-F01-E1-S02.pdf', 
                'FILE-F01-E1-S03.pdf', 
                'FILE-F01-E1-S04.pdf', 
                'FILE-F01-E1-S05.pdf', 
                'FILE-F02-E1-S01.pdf', 
                'FILE-F02-E1-S02.pdf', 
                'FILE-F02-E1-S03.pdf'
              ];

    $baseName        = '';
    $allSimilarNames = [];

    foreach($myArr as $index => &$name) {
      if($index == 0) {
          $baseName = substr($name, 0, strrpos($name, '-'));
          $allSimilarNames[] = $name;
      }
      else {
          if(strpos($name, $baseName) === 0) {
              $allSimilarNames[] = $name;
          }
      }
    }

    var_dump($allSimilarNames);

This will

Check at index one to get the base name to compare against
Loop all items in the array and match all items, no matter where in the array they are, that are similar according to your naming convention

So if you next time have an array that is

$myArr =  [ 
                    'FILE-F02-E1-S01.pdf',
                    'FILE-F01-E1-S01.pdf', 
                    'FILE-F01-E1-S02.pdf', 
                    'FILE-F01-E1-S03.pdf', 
                    'FILE-F01-E1-S04.pdf', 
                    'FILE-F01-E1-S05.pdf', 
                    'FILE-F02-E1-S02.pdf', 
                    'FILE-F02-E1-S03.pdf'
                  ];

this will return all the items that match FILE-F02-E1*.

You could also make a small function of it for easier use and not have to rely on the element at index 0 having to be the "base" name.

<?php
function findMatches($baseName, &$names) {
    $matches = [];
    $baseName = substr($baseName, 0, strrpos($baseName, '-'));
    foreach($names as &$name) {
        if(strpos($name, $baseName) === 0) {
          $matches[] = $name;
        }
    }

    return $matches;
}

$myArr =  [ 
            'FILE-F01-E1-S01.pdf', 
            'FILE-F01-E1-S02.pdf', 
            'FILE-F01-E1-S03.pdf', 
            'FILE-F01-E1-S04.pdf', 
            'FILE-F01-E1-S05.pdf', 
            'FILE-F02-E1-S01.pdf', 
            'FILE-F02-E1-S02.pdf', 
            'FILE-F02-E1-S03.pdf'
          ];

$allSimilarNames = findMatches('FILE-F01-E1-S01.pdf', $myArr);

var_dump($allSimilarNames);

Instead of testing `$index == 0` every time through the loop, why not just initialize `$baseName` using `$myArr[0]`? — Barmar, Sep 27 '18 at 19:13
@Barmar: I initially had the check since I was unsure that the item at index 0 should be part of the result. So I first never added that to the array. Then when I changed it I didn't refactor the code flow. That is why I added the example with making it a function instead since that is a "better" solution. The initial one with the reach was just a quick and dirty solution. — inquam, Sep 28 '18 at 07:02

The fourth bird · Answer 4 · 2018-09-27T20:11:04.093

You could get the first item from the array and use explode and implode to get the part from the filename without the last hyphen and the content after that.

Then use array_filter and use substr using 0 as the start position and the length of the $fileBeginning as the length to check if the string starts with FILE-F01-E1:

$array = [
    'FILE-F01-E1-S01.pdf',
    'FILE-F01-E1-S02.pdf',
    'FILE-F01-E1-S03.pdf',
    'FILE-F01-E1-S04.pdf',
    'FILE-F01-E1-S05.pdf',
    'FILE-F02-E1-S01.pdf',
    'FILE-F02-E1-S02.pdf',
    'FILE-F02-E1-S03.pdf',
    "TESTFILE-F01-E1-S03.pdf"
];
$parts = explode('-', $array[0]);
array_pop($parts);
$fileBeginning =  implode('-', $parts);
$secondArray = array_filter($array, function ($x) use ($fileBeginning) {
    return substr($x, 0, strlen($fileBeginning)) === $fileBeginning;
});
print_r($secondArray);

Result

Array
(
    [0] => FILE-F01-E1-S01.pdf
    [1] => FILE-F01-E1-S02.pdf
    [2] => FILE-F01-E1-S03.pdf
    [3] => FILE-F01-E1-S04.pdf
    [4] => FILE-F01-E1-S05.pdf
)

Demo

PHP group certain results from foreach on array into another array

4 Answers4