PHP Array

What is PHP array?

There are several basic variable types in PHP. Array is one of them. As everybody know due to its dynamic nature PHP does not require type definitions, and variables automatically appear when you mention them for the first time, and can change their type during execution.

Internally, PHP array, unlike array variables in classic static languages like C, is not a sequence of elements of one predefined type. PHP array is a hash table representing a reflection of keys to their values, where values can belong to any type. That is why you can easily modify PHP arrays, insert and remove their elements without need to repack the arrays' internal memory chunks. However, access time for PHP array remains O(1).

Despite the fact that PHP array is a hash, it has its beginning and its end. The keys which were defined first are closer to the beginning.

Basic PHP array functions

To point a PHP variable as array you should use the array() construction function.

The example above creates $myArray variable as an empty PHP array.

In general the construction looks like:

For example:

Key values in PHP array() function are optional. You can omit them. In this case PHP automatically assigns integer values starting with 0 to the array's keys. The following calls are equal:

If you skip some of the keys PHP will set them using the previously defined keys. The following calls are equal:

Check variable

You can always check whether a PHP variable is an array or not with help of is_array() function. It returns boolean true/false values which are usually used in conditions.

Access PHP array values

PHP uses the same syntax most popular languages use to access array values.

Put new variables into PHP array

There are several ways to add new values to array. The main is setting new value by key as shown in the example above where we added "children" key pointing to a newly created array of children's names.

The second way is operator []= which appends a new element to the end of array:

The third way is using functions like array_merge() and array_merge_recursive(), and + operator.

Get count of PHP array's elements

To find out how many elements there are in an array use count() function. It returns the amount of the first-level's elements.

Traveling through PHP array

If the array's keys are integers without gaps then the simplest way to go through it is for operator.

There is more advanced and more powerful foreach operator which covers all kinds of standard PHP arrays.

If you wish to get keys of your PHP array inside foreach together with the values use the following foreach syntax:

Both versions of foreach shown above iterate arrays getting $elementValue by value, which means that changing $elementValue inside foreach does not affect $userInfo itself. To get direct access to PHP array's values use the following syntax (mention the & sign):

Another way to iterate PHP arrays is the combination of reset(), list() and each() functions inside for operator. Here is how it looks like: