array_merge merges the elements of one or more arrays. array_combine Creates an array by using one array as its keys and another for its values.
“array_combine give an array by combining two arrays($keyArray, $valueArray) and both $keyArray & $valueArray must have same number of elements. $keyArrays become keys of returning Array, $valueArray become values of returning Arrays.
array_merge gives an array by merging two array ($array1, $array2) and both can have different number of elements. $array1 and $array2 are added in returning array.”