array_merge():- array_merge() function Merges the elements of one or more arrays together so that the values of one are appended to the end of the previous one. It returns the resulting array.
If the input arrays have the same string keys, then the value for that key of first array will overwrite by the value of next array. If, however, the arrays contain numeric keys, the later value will not overwrite the original value, but will be added at the last of the arrray.
array_combine() — Creates an array by using one array as its keys and another for its values
