What is an array in php? What types of arrays are there?

In PHP, an array is a collection of data, which organizes a series of data to form an operable whole. PHP arrays can be divided into three types: 1. Numeric index array; 2. Associative array; 3. Multidimensional array.

The operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

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What is an array

An array is a collection of data that organizes a series of data to form an operable whole. Arrays in PHP are complex but more flexible than arrays in many other high-level languages.

Array An array is an ordered set of variables, where each value is called an element. Each element is distinguished by a special identifier called a key (also called a subscript).

Each entity in the array contains two items, namely key and value. The corresponding array elements can be obtained by key value. These keys can be numeric keys or association keys. If a variable is a container that stores a single value, then an array is a container that stores multiple values.

PHP arrays are more flexible than arrays in other high-level languages. They not only support index arrays with numbers as keys, but also support associative arrays with strings or a mixture of strings and numbers as keys. In other high-level languages, such as Java or C, only numerically indexed arrays are supported.

You can use the following two methods to declare an array in PHP:

• You can declare an array by directly assigning values ​​to the array elements;

• Use the array() function to declare an array.

$数组变量名[下标] = 值;
$数组变量名 = array(key1 => value1, key2 => value2, ..., keyN => valueN);

What are the different types of arrays?

PHP arrays are divided into three categories

• Numeric index array:

  The index array stores a series of organized single or Multiple values, each of which can be accessed using an unsigned integer value.

• Associative array:

  "Associative array" is an array with a special indexing method. It can be indexed not only by integers, but also by strings or other types of values ​​(except NULL).

• Multi-dimensional array:

  The concept in data structure. Arrays above two-dimensional arrays, arrays that are neither linear nor plane, become multi-dimensional arrays.

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