What two types of arrays does PHP support?

PHP, as a server-side programming language, supports multiple data types, of which arrays are a very common one. Array in PHP is a composite data type that can store multiple values ​​and access these values ​​through keys. PHP supports two different types of arrays, namely indexed arrays and associative arrays.

1. Index array

Index array is the simplest and most common array type in PHP. It is a linear structure that uses numbers as keys to store ordered values.

The definition and assignment of index arrays can be completed in the following two ways:

Method one:

$array = array('value1', 'value2', 'value3');

Method two:

$array[0] = 'value1';
$array[1] = 'value2';
$array[2] = 'value3';

In the above example , we respectively define an index array containing three elements. In method one, we directly initialize the array with values, and these values ​​will be stored at index positions starting from 0 by default. In method two, we initialize the array by assigning values, and each value is specified through a numeric key.

In PHP, you can also use the range() function to create a fixed-length index array:

$array = range(1, 10);

The above code creates an index array containing the numbers 1 to 10.

Accessing the values ​​in the index array is also very simple, just use the key value:

echo $array[0]; // 输出：value1
echo $array[1]; // 输出：value2
echo $array[2]; // 输出：value3

2. Associative array

Associative array is also called Is a hash table or dictionary, which is another common PHP array type. Associative arrays use strings as keys to store unordered values. Each value is associated with a unique key through which we can access the corresponding value.

The definition and assignment of associative arrays can be completed in the following two ways:

Method one:

$array = array('key1' => 'value1', 'key2' => 'value2', 'key3' => 'value3');

Method two:

$array['key1'] = 'value1';
$array['key2'] = 'value2';
$array['key3'] = 'value3';

In the above example , we respectively define an associative array containing three elements. In method one, we initialize the array through the "key => value" method. In the second method, we initialize the array by assigning values, and each value is specified by a string key.

Accessing the values ​​in the associative array is also very simple, just use the key value:

echo $array['key1']; // 输出：value1
echo $array['key2']; // 输出：value2
echo $array['key3']; // 输出：value3

It should be noted that in PHP, string keys are not case-sensitive, that is Say, "key1" and "KEY1" can both be used as array keys.

Summary

PHP supports two basic array types: indexed arrays and associative arrays. Indexed arrays use numbers as keys to store ordered values; associative arrays use strings as keys to store unordered values. These two array types can be defined, assigned, and accessed in different ways. Proficiency in the use of arrays is very important for PHP developers.

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