What three parts does a php array consist of?

The three components of the php array: 1. "Array name". An array is an ordered sequence of variables. If a limited set of variables of the same type is named, then this name is the array name; 2 , "value", that is, each element stored in the array; 3. "key", each element is distinguished by a special identifier, which is called a key (also called a subscript).

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

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

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, before "=>" The value (0, 1, 2, 3...) is the key (subscript), and 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 the name of the variable part;

• must start with a letter or underscore;

• cannot start with a number;

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

• Unlike other languages, some keywords in PHP can also be used as Variable name (e.g. $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

• String or a mixture of strings and numbers

An index array with numbers as keys, and 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 an array element in the array There is no need to specify the position. PHP will automatically assign an integer value to the key name of the index array, and then automatically increase 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 numeric values ​​and strings. If there is a key name in an array that is not numbers, then this array is an associative array.

If the key name is a string, use a delimiting modifier for the key name - single quotes '' or double quotes "" pack.

<?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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