skip first value for variable inside of foreach loop php

Based on OP's comments, $Pt is an array of array. So we simply use array_shift to remove the first value (second level array). And, append an array of static value to the end:

$vid_pix = get_post_meta($v_Id, 'vid_pix', false);

foreach ($vid_pix as $vP) {
    $Pt = get_post_meta($vP, 'photo_time', false);

    // $Pt is an array of array
    // remove the first key (first array)
    $first_key = array_shift($Pt);

    // Add the static value to end of the array. eg: '5'
    $static_value = '5'; // define static value
    $Pt[] = array($static_value);

    // print them out
    var_dump($Pt);
}

Why not to do it in the simplest way?

$keys = array_keys($myHashArray);
$values = array_values($myHashArray);
array_shift($keys);
array_shift($values);
$result = array_combine($keys, $values);

Please correct me if I understood it wrong.

you could simply proceed like this:

$static_value=25;
$array=['vp 1'=>5,'vp 2'=>10,'vp 3'=>15,'vp 4'=>20];

reset($array);//reset the internal pointer
while(false!==($key=key($array))&&null!==key($array)){//check for current key validity
    $next=next($array);//get the next value and move the pointer
    $array[$key]=$next&&isset($array[$key])?$next:$static_value;//assign the next value to the current key  if valid or the static value if false 
}


var_dump($array);

output :

array(4) {
  ["vp 1"]=>
  int(10)
  ["vp 2"]=>
  int(15)
  ["vp 3"]=>
  int(20)
  ["vp 4"]=>
  int(25)
}

How about ?

$new_array = array_combine( // to make an array from $keys / values
  array_keys($old_array), // use the old same keys
  array_merge( // the array containing your new values
    array_splice($old_array, 1), // remove the first element
    [$static_value] // add the static value
  )
);

Check it in live here : https://repl.it/repls/PerfectUpsetAnalysts

$vid_pix = get_post_meta($v_Id, 'vid_pix', false);
$i = 0;
foreach ($vid_pix as $vP) {
   if($i ==0){
continue;
}
    $Pt = get_post_meta($vP, 'photo_time', false);
    array_splice($Pt, 0, 1);
    //unset($Pt[0]);
    $Pt = get_post_meta($vP, 'photo_time', true);
    echo $Pt;

    if (last -> $Pt) { // something like this for the last value
        $Pt = '5';
    }
$i++;
 }

use this type of counter for skipping value....

As you already know you are getting photo_time of each vid_pix and in your question I see you need to get photo_time of next vid_pix for current vid_pix and ignore the first photo_time which is 5 in provided example and the last vid_pix (put something static instead)

[vp 1]->[5]
[vp 2]->[10]
...

I would need -

[vp 1]->[10]
[vp 2]->[15]
...

so I think its simple (I use vip_pix index as key, you can use whatever)

$pt_result = [];
for ($i = 0; $i < count($vid_pix) - 1; ++$i) {
    $pt_result[$vid_pix[$i]] = get_post_meta($vid_pix[$i+1], 'photo_time', true);
}
$pt_result[$vid_pix[$i]] = 25; //set last one statically

You need to shift the array outside the loop since your $Pt array has single value. Try the code given below.

$newPt = array(); // initialize new array
$vid_pix = get_post_meta($v_Id, 'vid_pix', false);

foreach ($vid_pix as $vP) {
    $Pt = get_post_meta($vP, 'photo_time', false);

    // assign to new array
    $newPt[] = $Pt;
}

// remove first value
array_shift( $newPt );

// add static value to end of the array
$static = '5';
$newPt[] = array( $static );

// print updated array
var_dump($newPt);

Hope this helps.

How about passing the results of get_post_meta($vP, 'photo_time', false); into a function that shifts the values and adds the static value to the end?

function shiftPt($input, $end = null) {
    $output = [];
    $prevKey = null;
    foreach ($input as $key => $value) {
        if ($lastKey) $output[$lastKey] = $value;
        $lastKey = $key;
    }
    $output[$key] = $end;
    return $output;
}

So essentially you could just wrap your existing function like so...

$pT = shiftPt(get_post_meta($vP, 'photo_time', false));

... and this would leave the last value in the array as null while shifting all of the original values up.

If you wanted to specify the final value (e.g. as 5) then you could do...

$pT = shiftPt(get_post_meta($vP, 'photo_time', false), 5);

You can use array_slice to remove one set of value from the array and use array_merge to merge it with the "x".

Then you just combine the keys and "new" values.

$arr = [
'vp 1'=>[5],
'vp 2'=>[10],
'vp 3'=>[15],
'vp 4'=>[20]];

$keys = array_keys($arr);
$values = array_merge(array_slice($arr, 1), ["x"]);

$new = array_combine($keys, $values);
var_dump($new);

This outputs:

array(4) {
  ["vp 1"]=>
  array(1) {
    [0]=>
    int(10)
  }
  ["vp 2"]=>
  array(1) {
    [0]=>
    int(15)
  }
  ["vp 3"]=>
  array(1) {
    [0]=>
    int(20)
  }
  ["vp 4"]=>
  string(1) "x"
}

https://3v4l.org/l7NBa