shift array without indexOfOutBounds - php

Question

I have 2 array's with the same length. array $gPositionStudents and array $gPositionInternships. Each student is assigned to a different internship, That part works.
Now I want the first element (index 0) of $gPositionStudent refer to the second (index 1) element of array $gPositionInternship. That implicitly means that the last element of $gPositionStudents refer to the first element of $gPositionInternship. (I included a picture of my explanation).
My Code is:
// Make table
$header = array();
$header[] = array('data' => 'UGentID');
$header[] = array('data' => 'Internships');
// this big array will contains all rows
// global variables.
global $gStartPositionStudents;
global $gStartPositionInternships;
//var_dump($gStartPositionInternships);
$rows = array();
$i = 0;
foreach($gStartPositionStudents as $value) {
foreach($gStartPositionInternships as $value2) {
// each loop will add a row here.
$row = array();
// build the row
$row[] = array('data' => $value[0]['value']);
//if($value[0] != 0 || $value[0] == 0) {
$row[] = array('data' => $gStartPositionInternships[$i]);
}
$i++;
// add the row to the "big row data (contains all rows)
$rows[] = array('data' => $row);
}
$output = theme('table', $header, $rows);
return $output;
Now I want that I can choose how many times, we can shift. 1 shift or 2 or more shifts. What I want exists in PHP?

Answer 1

Something like this:
//get the array keys for the interns and students...
$intern_keys = array_keys($gStartPositionInternships);
$student_keys = array_keys($gStartPositionStudents);
//drop the last intern key off the end and pin it to the front.
array_unshift($intern_keys, array_pop($intern_keys));
//create a mapping array to join the two arrays together.
$student_to_intern_mapping = array();
foreach($student_keys as $key=>$value) {
$student_to_intern_mapping[$value] = $intern_keys[$key];
}
You'll need to modify it to suit the rest of your code, but hopefully this will demonstrate a technique you could use. Note the key line here is the one which does array_unshift() with array_pop(). The comment in the code should explain what it's doing.

Answer 2

I think you want to do array_slice($gPositionsStudents, 0, X) where X is the number of moves to shift. This slices of a number of array elements. Then do array_merge($gPositionsStudents, $arrayOfSlicedOfPositions); to append these to the end of the original array.
Then you can do an array_combine to create one array with key=>value pairs from both arrays.