Can php always-on be an array?

Constants in PHP are immutable variables and cannot be modified once defined. Constants use their names when defined as identifiers, usually represented by capital letters. In order to increase the readability and maintainability of the code, the values ​​of constants are generally fixed, such as values ​​of simple types such as numeric values ​​and characters.

You can define a constant as follows:

define("PI", 3.1415926);
echo PI;

The output result is:

3.1415926

A constant is a simple value and cannot contain expressions, so a constant cannot be defined as an array type.

However, PHP provides a constant array, which can achieve array-like functions through array constants, which is very useful in certain situations.

Define a constant array:

define("FRUITS", [
  "apple",
  "orange",
  "banana"
]);
 
echo FRUITS[1];

The output is:

orange

In this example, FRUITS is a constant array, enclosed in square brackets. The way to access array elements is the same as a normal array. You can use subscripts to access array elements, such as FRUITS[1].

It is important to note that in PHP 5.6 and below, you can only use the define function to define constant arrays, while in PHP 7.0 and above, you can use the const keyword to define constant arrays.

For example, define a constant array:

const ANIMALS = [
    'dog',
    'cat',
    'bird'
];
echo ANIMALS[2];

The output result is:

bird

The advantage of a constant array is that it can be reused throughout the application and avoids the complexity of remembering value, and the fixity of the value can be guaranteed.

In general, PHP constants are a very convenient tool that can help reduce hard codes in the code and improve the readability and maintainability of the code. Although PHP constants cannot be directly defined as arrays, PHP provides the function of constant arrays, which can implement array-like functions and meet some specific needs.

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