How to assign to each output values from foreach loop to a meta_key?

Question

For a custom plugin with add start and end date of event/post, I must generate several datetime with the same meta key to compare the period of event with the period of weeks. I my case I'm obliged to compare each day date of event with these of period because the 'key'=>of meta_query can't be a array. The user will have the choice with current week, week +1 and week+ 2 and 3.

I created a script to generate all days between start and end of event. Depending on my custom plugin script to add/update several _post_meta(), I include each meta key inside an array.

The period event is from 12 to 28 September : my script generate these date :

2023-09-12 00:00:00
2023-09-13 00:00:00
2023-09-14 00:00:00
2023-09-15 00:00:00
2023-09-16 00:00:00
2023-09-17 00:00:00
2023-09-18 00:00:00
2023-09-19 00:00:00
2023-09-20 00:00:00
2023-09-21 00:00:00
2023-09-22 00:00:00
2023-09-23 00:00:00
2023-09-24 00:00:00
2023-09-25 00:00:00
2023-09-26 00:00:00
2023-09-27 00:00:00
2023-09-28 23:59:59

Each date ($date) is converted into a datetime to obtain a timestamp. In meta_query these dates are compared with those of the selected week :

from 2023-09-18 00:00:00 to 2023-09-24 00:00:00

How can I output these datetime allocating a variable to each to obtain as many times this variable as there are dates generated $events_meta['timestamps_between'] = strtotime($date);

foreach ($period as $date) {
    $events_meta['timestamps_between'] .= strtotime($date);
}

My script call many meta_key and I called them inside this foerreach :

foreach ( $events_meta as $key => $value ) {
    add_post_meta( $post->ID, $key, $value );
    //if($key = 'timestamps_between'){
        //print_r($key .' and '. $value); 
    //}
}

Online test

Answer 1

Problem Solved but solution not reusable.

I'd like some advice or a solution to assign the same meta_key to each datetime generated.

Based from this answer : to assign variables to each datetime from foreach loop I do that (but I think it's a bad idea to change the name of the array keys using the is_int() function to target the key integers):

1. create an array ($events_meta)
2. Inside a foreach loop, call the dates of DatePeriod

My solution is only usable because I only use is_int for the 'timestamps_between' meta_key.

$start = $beginOfDayObject;
$interval = new DateInterval('P1D');
$end = $excludeObject;
$period = new DatePeriod($start, $interval, $end);

$events_meta = array();
foreach ($period as $date) {
    $events_meta[] = $periodtotime."\n";
}

each new meta_key will be read by this foreach loop: (The condition using is_int() allow to replace all keys integer by the meta_key.)

foreach ( $events_meta as $key => $value ) {
        if(is_int($key) ) $key ='timestamps_between';
         add_post_meta( $post->ID, $key, $value );
}