difference between array merge and combine

• 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). 

• 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)