An array in PHP is a data structure that allows you to store multiple values of similar data type in a single variable. In PHP, an array is actually an ordered map that associates values to keys. There are three types of arrays in PHP:

• Indexed arrays: These are arrays with a numeric index. Values are stored and accessed in linear fashion.
• Associative arrays: These are arrays with named keys. This stores element values in association with key values rather than in a strict linear index order.
• Multidimensional arrays: These are arrays containing one or more arrays and values are accessed using multiple indices.

To create an array in PHP, you can use the array() function. For example, to create an indexed array, you can use the following code:

$numbers = array(1, 2, 3, 4, 5);

To access the elements of an array, you can use the index number or key name. For example, to access the first element of the above array, you can use the following code:

echo $numbers[0];

To get the length of an array, you can use the count() function. For example, to get the length of the above array, you can use the following code:

echo count($numbers);

Arrays can hold different types of values, including numbers, strings, and objects.