/**
* Figure out which columns in a table have been added, removed, or changed.
*
* @param Table $old The original table
* @param Table $new The new table
* @return array A 3-element array (tuple) of added, dropped, and changed columns.
*/
public static function columnDiff(Table $old, Table $new)
{
/* Index of columns in the table's new state */
$newCols = [];
foreach ($new->columns as $idx => $column) {
$newCols[$idx] = $column->name;
}
/* Index of columns in the table's old state */
$oldCols = [];
foreach ($old->columns as $idx => $column) {
$oldCols[$idx] = $column->name;
}
/* Drop any tables that are in the old and not the new */
$drop = [];
foreach (array_diff($oldCols, $newCols) as $dropName) {
$drop[] = $old->getColumnByName($dropName);
}
/* Add columns that are in the new but not the old */
$add = [];
foreach (array_diff($newCols, $oldCols) as $addName) {
$add[] = $new->getColumnByName($addName);
}
/* Compare any common columns, and modify if unequal */
$change = [];
foreach (array_intersect($newCols, $oldCols) as $commonName) {
$newCol = $new->getColumnByName($commonName);
$oldCol = $old->getColumnByName($commonName);
if ($newCol && $oldCol && !$newCol->equals($oldCol)) {
$change[] = [$oldCol, $newCol];
}
}
return [$add, $drop, $change];
}
