Arrays are indexed from 0.
Not necessay to add indexes:
Associate Arrays - using strings as indexes
Arrays in php are all associate - if you remove one value the indexes are not recalculated. The last values added are the last in the array whatever there index value.
Use 'unset' to remove single array values or the entire array.
You can mix data types in an array.
PHP allows the creation of two dimensional arrays
To output array values loop through them with foreach()