php comma separated array cannot be separated

In PHP, converting a string into an array is a very common operation. Normally, we can use the string splitting function explode() to split a string using a specified character as the delimiter, and then put the split substrings into an array.

For example, the following code will split the string 1,2,3,4,5 according to commas and store it in an array:

$str = "1,2,3,4,5";
$arr = explode(",", $str);
print_r($arr); // 输出 Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 )

However , we may encounter some strange problems in actual development. For example, in some cases, comma-delimited strings cannot be split normally, resulting in the inability to obtain the correct number and value of array elements.

So how do these problems arise? Let’s discuss it in detail below.

Cause of the problem

In PHP code, commas are often used as delimiters. However, in some cases, the comma may represent more than a single character, such as multi-byte characters or special control characters.

If a string contains these special characters, you need to be more careful when using explode() to split. Here are some specific examples to illustrate.

Multi-byte characters

In the MySQL database, certain field types are often specified as Chinese character sets, such as utf8 or utf8mb4. Some characters in these character sets may be multi-byte, such as "Chinese characters" which require three bytes of space to store.

If we try to split a string consisting of multi-byte characters, we may encounter some problems. In some cases, some extra characters will be automatically added between specific segmentation characters, resulting in segmentation errors.

The following is an example:

$str = "中,文,汉,字";
$arr = explode(",", $str);
print_r($arr); // 输出 Array ( [0] => 中 [1] => 文í [2] => åŒ [3] => å­ )

As you can see, errors will occur after splitting a string composed of multi-byte characters. This is because when PHP processes multi-byte characters, it needs to convert its encoding into binary format before processing. There may be differences between the converted binary characters and the original characters, resulting in incorrect segmentation results.

Special characters

In addition to multi-byte characters, there are some special characters that may also cause segmentation errors. For example, when performing a split operation on a string consisting of carriage returns and line feeds, some strange problems may occur.

The following is an example:

$str = "a,
,b,
,c";
$arr = explode(",
", $str);
print_r($arr); // 输出 Array ( [0] => a [1] => b [2] => c )

In this example, because the string contains carriage returns and line feeds, when trying to split by `,
` Some problems will arise. Specifically: some spaces will be added between the dividing characters, different operating systems and text editors handle carriage returns and line feeds differently, etc.

So, in this case, we can try to use regular expressions for more precise matching and segmentation.

Solution

In order to avoid the problem that comma-delimited strings cannot be split correctly, we can try to use some specific functions to solve it.

preg_split function

Use the PHP built-in function preg_split() to easily perform regular expression matching and splitting. The following is an example of splitting using preg_split():

$str = "a,
,b,
,c";
$arr = preg_split('/,
/', $str);
print_r($arr); // 输出 Array ( [0] => a [1] => b [2] => c )

As you can see, after using preg_split() to split a comma-separated string, you get The results are consistent with the previous example.

Since the preg_split function is based on regular expression matching and splitting, it can be applied to different string content and delimiter scenarios.

mb_split function

Another feasible solution is to use the PHP built-in function mb_split() to perform the split operation. Unlike preg_split(), mb_split() does not rely on regular expressions for splitting.

The following is an example of splitting using the mb_split() function:

$str = "中,文,汉,字";
$arr = mb_split(",", $str);
print_r($arr); // 输出 Array ( [0] => 中 [1] => 文 [2] => 汉 [3] => 字 )

As you can see, using mb_split() section characters, the result is correct.

Summary

In PHP, converting a comma-delimited string into an array is a common operation. However, in actual development, we may encounter some special circumstances, such as multi-byte characters, special characters, etc., resulting in the comma-separated array element values ​​being unable to obtain correct values.

In order to avoid these problems, we can try to use the PHP built-in function preg_split() or mb_split() to perform string splitting operations. Both methods can solve the problem of comma-delimited strings not being split correctly, and provide different advantages suitable for different scenarios.

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