In the context of PHP, keys and values are fundamental concepts used to represent and access data in various data structures, such as arrays and associative arrays (also known as dictionaries or hash tables).
Keys
A key is a unique identifier that is used to access a specific value within a data structure. Keys can be of different data types, such as integers, strings, or even objects. They serve as the index or label for each value stored in the data structure.
In PHP, keys are used extensively in arrays. When you create an array, each element is assigned a key, which can be either an integer (for indexed arrays) or a string (for associative arrays). For example:
$fruits = array("apple", "banana", "cherry");
// Keys are automatically assigned as integers: 0, 1, 2
