difference between array merge and combine

array_merge() combines one or more arrays by appending elements, while array_combine() creates a new array from two separate arrays: one for the keys and one for the values. array_merge() is used to join arrays together, while array_combine() uses one array to create the keys and another to supply the values for a new array.

array_merge()

Function: Joins one or more arrays into a single array.
Behavior:
- For numeric keys, it appends the values and re-indexes them starting from zero.
- For string keys, if a key exists in more than one array, the value from the later array overwrites the earlier one.
Example: array_merge(array(1, 2), array(3, 4)) results in array(1, 2, 3, 4).

array_combine()

Function: Creates a new array using one array for keys and another for values.
Behavior:
- It requires both input arrays to have the same number of elements.
- If the key array is empty or the value array is empty, it will produce an error.
Example: array_combine(array('a', 'b'), array(1, 2)) results in array('a' => 1, 'b' => 2)