We mentioned that arrays can hold elements of any type—this even includes other arrays! We can use chained operations to access and change elements within a nested array:

$nested_arr = [[2, 4], [3, 9], [4, 16]]; $first_el = $nested_arr[0][0]; echo $first_el; // Prints: 2

Above, $nested_arr is an array with three array elements. The first, located at the 0th index, is the array [2, 4]. The expression $nested_arr[0] returns that array. We then index that array’s first element by appending an additional [0].

This can take practice to get used to. One helpful technique is to act like the computer; evaluate each part of the expression from left to right. By breaking down a complex expression into its simpler parts, it becomes easier to understand. Let’s walk through a more complicated example together:

$very_nested = [1, "b", 33, ["cat", 6.1, [9, "LOST!", 6], "mouse"], 7.1];

We want to change the element which is currently "LOST!" to "Found!". Let’s breakdown the steps:

  • We need the outermost array first: $very_nested[3] evaluates to the array ["cat", 6.1, [9, "LOST!", 6], "mouse"]
  • Next we need the array located at the 2nd location index: $very_nested[3][2] evaluates to the array [9, "LOST!", 6]
  • And finally, the element we’re looking for: $very_nested[3][2][1] evaluates to "LOST!"
    $very_nested[3][2][1] = "Found!";

Let’s get some more practice with nested arrays!



We’re going treasure hunting! Hidden within this terribly nested array is the string "GOLD!". Your job is use echo to print it to the terminal. The trick: you must use array indexing to accomplish this goal. It’s up to you whether you do this in one step or break it down into multiple steps.

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