What three parts does a php array consist of?

php array consists of three parts: "array name", "value" and "key". They are: 1. Array name. An array is an ordered sequence of variables. If a limited set of variables of the same type is named, then the name is the array name; 2. Value, which is the individual elements stored in the array; 3. Key. Each element is distinguished by a special identifier. This identifier is called a key, also called a subscript.

The operating environment of this tutorial: Windows 10 system, PHP8.1.3 version, Dell G3 computer.

php array consists of three parts: "array name", "value" and "key".

Example:

<?php header(&#39;content-tyPE:text/htML;charset=utf-8&#39;);   
$array=array(1,2,3,4,5,6,7,8,9,10);
echo "第一个元素：".$array[0];
var_dump($array);//打印数组
?>

In the above example: $array is the array name, and the value before "=>" (0, 1, 2, 3...) is the key (subscript), the value (1, 2, 3...) after "=>" is the value.

1. Array name

An array (Array) is an ordered sequence of elements. If a limited collection of variables of the same type is named, then the name is the array name.

Array name naming follows certain rules (same as variable names):

must start with the $ symbol, followed by the name of the variable, $ is not part of the variable name;

must start with a letter or underscore;

cannot start with a number;

can only contain letters (A~z), numbers (0~9) and underscores (_);

Unlike other languages, some keywords in PHP can also be used as variable names (such as $true, $for).

Note: Variable names in PHP are case-sensitive, so $VAR and $Var represent two different variables.

2. Key name and key value

Array 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).

In PHP, key names can be divided into two types:

Pure numbers

Strings or mixed strings and numbers

Use numbers as key names An index array, an associative array with strings or a mixture of strings and numbers as keys.

1) Index array

The subscript (key name) of the index array consists of numbers, starting from 0 by default. Each number corresponds to the position of an array element in the array. There is no need to specify Specified, PHP will automatically assign an integer value to the key name of the index array, and then automatically increment from this value.

For example, the example given at the beginning is an index array.

2) Associative array

The subscript (key name) of the associative array is composed of a mixture of numerical values ​​and strings. If a key name in an array is not a number, then the array is Associative array.

If the key name is a string, the key name must be wrapped with a delimiting modifier - single quote '' or double quote "".

<?php header(&#39;content-type:text/html;charset=utf-8&#39;);   
$array=array("id"=>1,"name"=>"李华","age"=>23,"1"=>1,"id2"=>52);
echo "键名为name的元素：".$array["name"];
var_dump($array);//打印数组
?>

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