I get an array with file ('file.txt') , a file like this:

"Monday 21 August
...
...
Tuesday
...
...
Wednesday 23 August
... "

I need to split the array by day of the week (regex array):

$ days = array (
    '/ ^ Monday + /',
    '/ ^ Tuesday + /',
    '/ ^ Wednesday + /',
    '/ ^ Thursday + /',
    '/ ^ Friday + /',
    '/ ^ Saturday + /',
    '/ ^ Sunday + /',
);

If there are 7 days, then file () will turn into 7 arrays. I can find the keys of the days of the week using preg_grep, which occurs in file () … If you had to make 2 arrays from one, you could use array_slice. But what if there can be 7 or more of them?

Answer 1, authority 100%

Alternatively, you can bring it to perfection yourself:

& lt;? php
$ array [0] = 'Monday day';
$ array [1] = '12';
$ array [2] = '12';
$ array [3] = 'Tuesday day';
$ array [4] = '45';
$ array [5] = '45';
$ array [6] = 'Wednesday afternoon';
$ array [7] = '789';
$ array [8] = '789';
$ array [9] = '789';
$ now = -1;
$ response = array ();
foreach ($ array as $ key = & gt; $ value) {
   if (preg_match ('/ ^ Monday + | ^ Tuesday + | ^ Wednesday + /', $ value)) {
     $ now ++;
   } else {
     if ($ now & gt; -1)
        $ response [$ now] [] = $ value;
   }
}
print_r ($ response);

Then figure it out for yourself, the answer is:

Array
(
  [0] = & gt; Array
    (
      [0] = & gt; 12
      [1] = & gt; 12
    )
  [1] = & gt; Array
    (
      [0] = & gt; 45
      [1] = & gt; 45
    )
  [2] = & gt; Array
    (
      [0] = & gt; 789
      [1] = & gt; 789
      [2] = & gt; 789
    )
)

Answer 2

Greetings! Perhaps the solution is not the most elegant, if anything, modify it yourself! 😉

Text in file:

Monday, August 21
Server is running
Tuesday 22 August
Server crashed
Wednesday 23 August
Server is running
Server is running
Wednesday 24 August
Server crashed
Tuesday 25 August

$ text_arr = file ("t.txt");
$ days = [
  '/ ^ Monday + /',
  '/ ^ Tuesday + /',
  '/ ^ Wednesday + /',
  '/ ^ Thursday + /',
  '/ ^ Friday + /',
  '/ ^ Saturday + /',
  '/ ^ Sunday + /',
];
$ keys = [];
$ result = [];
/ **
 * We iterate over the array of patterns and check the occurrences in the text
 * cutting off empty elements, and write in $ keys the ordinal number of the line with the date
 * All subsequent id between them, our future arrays with text.
 * At the output, we get an array of the form:
 * [0] = & gt; int (0) [1] = & gt; int (2) [2] = & gt; int (9) [3] = & gt; int (4) [4] = & gt; int (7) ...
 * /
foreach ($ days as $ day):
  $ search = preg_grep ($ day, $ text_arr);
  if (! empty ($ search)):
    foreach ($ search as $ id = & gt; $ chunk):
      array_push ($ keys, $ id);
    endforeach;
  else:
    continue;
  endif;
endforeach;
/ ** Sort the array by values, in order, since we will parse the text from top to bottom * /
sort ($ keys);
/ **
 * Increase our id by 1 in order not to include dates in the result
 * Trim the array by indentation, where the starting indent will be the id found above,
 * and the length of the indentation will be the difference between the id of the next element and the current one.
 * /
foreach ($ keys as $ id = & gt; $ key):
  ++ $ key;
  if (++ $ id! = count ($ keys)):
    array_push ($ result, array_slice ($ text_arr, $ key, next ($ keys) - $ key));
  else:
    array_push ($ result, array_slice ($ text_arr, $ key));
  endif;
endforeach;

Result:

array (5) {
 [0] = & gt;
 array (1) {
  [0] = & gt;
  string (31) "Server is running"
 }
 [1] = & gt;
 array (1) {
  [0] = & gt;
  string (23) "Server crashed"
 }
 [2] = & gt;
 array (2) { 
[0] = & gt;
   String (31) "The server works
"
   [1] = & gt;
   String (31) "Server running"
  }
  [3] = & gt;
  Array (1) {
   [0] = & gt;
   String (23) "Server Fell"
  }
  [4] = & gt;
  Array (0) {
  }
}