How to convert string to array in PHP

In PHP, strings and arrays are one of the most commonly used data types. A string is usually data consisting of a set of characters, while an array is a data structure consisting of an ordered list of data. In PHP, sometimes we need to convert a string into an array in order to perform more flexible operations on the data in it. This article will introduce how to convert a string to an array in PHP and explore its related issues under UTF-8 encoding.

1. PHP string to array

Converting string to array in PHP can be achieved through a variety of methods, such as functions such as explode(), str_split() and preg_split(). Two of these methods are introduced below.

1. Use the explode() function

The explode() function is a common way to convert a string into an array in PHP. Its syntax is as follows:

array explode(string $delimiter, string $string [, int $limit = PHP_INT_MAX])

Among them, $delimiter is the identifier of the split string, $string is the string to be split, and $limit is the maximum number of units returned (default is PHP_INT_MAX).

For example, we have a string $str whose content is:

$str = "apple,banana,orange";

We can convert it into an array with commas as delimiters, the code is as follows:

$arr = explode(",", $str);
print_r($arr);

The output result is:

Array
(
    [0] => apple
    [1] => banana
    [2] => orange
)

2. Use str_split() function

str_split() function can convert a string into a character array, its syntax is as follows:

array str_split(string $string [, int $split_length = 1])

Among them, $string is the string to be converted, $split_length is an optional parameter, specifying the length of each character, the default is 1 character.

For example, we have a string $str, whose content is:

$str = "hello world";

We can convert it into a character array, the code is as follows:

$arr = str_split($str);
print_r($arr);

The output result is ：

Array
(
    [0] => h
    [1] => e
    [2] => l
    [3] => l
    [4] => o
    [5] =>
    [6] => w
    [7] => o
    [8] => r
    [9] => l
    [10] => d
)

2. Problems with character encoding and UTF-8 encoding

When we use the above method to convert a string into an array, we need to pay attention to the character encoding issue. Because the length (number of bytes) of a character is different under different character encodings, this will cause problems using the str_split() function under UTF-8 encoding.

Under UTF-8 encoding, a Chinese character usually occupies 3 bytes, and an English character occupies 1 byte. Therefore, if we use the str_split() function to convert a UTF-8 encoded string into an array, character splitting errors will occur.

For example, we have a UTF-8 encoded string $str whose content is:

$str = "中文test";

We want to convert it into a character array, but if we use str_split() directly function, the following results will be obtained:

Array
(
    [0] => 中
    [1] => 文
    [2] => t
    [3] => e
    [4] => s
    [5] => t
)

It can be seen that the Chinese characters are incorrectly split into two characters.

To solve this problem, we can use the mb_str_split() function. This function is a supplement to the str_split() function and supports the splitting of multi-byte characters. Its syntax is as follows:

array mb_str_split(string $string [, int $split_length = 1 [, string $encoding = mb_internal_encoding()]])

Among them, $string is the string to be converted, $split_length is an optional parameter, specified The length of each character, the default is 1 character, $encoding is an optional parameter, specifies the character encoding, the default is mb_internal_encoding().

For example, we can use the following code to convert the above string $str into an array:

$arr = mb_str_split($str);
print_r($arr);

The output result is:

Array
(
    [0] => 中
    [1] => 文
    [2] => t
    [3] => e
    [4] => s
    [5] => t
)

The result is correct.

3. Summary

In PHP, converting a string to an array is a common operation. We can do this using explode() or str_split() function. However, under UTF-8 encoding, you need to pay attention to the character length problem, which can be solved using the mb_str_split() function. At the same time, we can also use other functions, such as preg_split(), etc. In actual use, appropriate functions and methods need to be selected according to specific situations.

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