Several representations of php arrays

PHP is a very popular programming language, and one of its important features is its support for arrays. Array is a very useful data structure that can be used to store a group of related data, and its elements can also be accessed through subscripts. In PHP, arrays have many different representation methods. This article will briefly introduce several common representation methods and how to use them.

1. Index array

The index array is the most basic array type in PHP and the most commonly used one. Its characteristic is that the array elements have a numeric subscript, and the subscripts start from 0 and increase continuously. If we want to create an index array, we can use the following syntax:

$array = array('apple', 'banana', 'orange');

In this array, the subscript of 'apple' is 0, 'banana' The subscript of is 1, and the subscript of 'orange' is 2. We can access the elements in the array through subscripts, such as:

echo $array[0];  // 输出：'apple'
echo $array[2];  // 输出：'orange'

In addition to using the above syntax, we can also use the simplified syntax to create indexed arrays:

$array = ['apple', 'banana', 'orange'];

In PHP5. 4, this simplified syntax has become an officially supported syntax.

2. Associative array

Different from the index array, the subscript of the associative array is not of numeric type, but of string type. Associative arrays use strings as subscripts, so they are accessed differently. We can use the following syntax to create an associative array:

$array = array('name' => 'Tom', 'age' => 18, 'city' => 'Beijing');

In this array, the value of the subscript 'name' is 'Tom', the subscript The value of 'age' is 18, and the value of subscript 'city' is 'Beijing'. We can access elements in the array through subscripts, such as:

echo $array['name'];  // 输出：'Tom'
echo $array['city'];  // 输出：'Beijing'

Similar to indexed arrays, associative arrays can also be created using simplified syntax:

$array = ['name' => 'Tom', 'age' => 18, 'city' => 'Beijing'];

3. Multidimensional array

In PHP, in addition to creating one-dimensional arrays, we can also create multi-dimensional arrays. A multidimensional array is a nested array that can be used to store more complex data. We can use the following syntax to create a two-dimensional array:

$array = array(
    array('apple', 'banana', 'orange'),
    array('red', 'yellow', 'orange'),
    array('big', 'small', 'medium')
);

In this array, the array elements themselves are also arrays. We can access elements in the array through multiple subscripts, such as:

echo $array[0][0];  // 输出：'apple'
echo $array[1][2];  // 输出：'orange'

In actual development, we can also create arrays with more dimensions, such as three-dimensional arrays, four-dimensional arrays, and so on. However, it should be noted that multi-dimensional arrays need to be used with caution, otherwise the code will become cluttered.

4. Array splicing

In addition to the several array representation methods introduced above, PHP also provides a very convenient array splicing method. We can use the array_merge() function to merge two arrays into a new array, such as:

$array1 = array('apple', 'banana', 'orange');
$array2 = array('red', 'yellow', 'green');
$array3 = array_merge($array1, $array2);
print_r($array3);

Output:

Array
(
    [0] => apple
    [1] => banana
    [2] => orange
    [3] => red
    [4] => yellow
    [5] => green
)

In this code, we will Arrays $array1 and $array2 are merged into a new array $array3 through the array_merge() function, and then use print_r ()The function outputs the contents of this new array.

Summary

Arrays are one of the very important data types in the PHP language. Mastering several different array representation methods is very helpful for developing PHP applications. In actual development, we can flexibly use different array types and methods to store and process data to achieve more powerful and efficient applications.

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