PHP function introduction: mb_substr()

PHP is a widely used programming language with powerful functions and extremely high flexibility, and its functions are also one of the important tools to improve programming efficiency. Today we are going to introduce a very useful function in PHP: mb_substr().

The mb_substr() function is a string interception function in PHP. It can intercept a part of a multi-byte string and return the intercepted new string. Different from the ordinary substr() function, mb_substr() can correctly handle multi-byte characters (such as Chinese, Japanese, etc.), ensuring that the intercepted string will not be garbled or inaccurate. This is useful for reading and writing text in international projects.

mb_substr() function format is as follows:

string mb_substr ( string $str , int $start [, int $length [, string $encoding ]] )

Among them, $str represents the string to be intercepted, $start represents the starting position of interception (starting from 0), and $length represents the string to be intercepted. The length of $encoding indicates the string encoding method, which defaults to the character encoding method of the current script (usually UTF-8).

Let’s look at some specific usage examples:

Example 1:

$str = "今天是个好日子";
echo mb_substr($str, 0, 2);  // 输出“今天”

Explanation: Since Chinese characters occupy 2 bytes, the first 2 characters are intercepted. "Today" is available.

Example 2:

$str = "abcdefg你好";
echo mb_substr($str, 1, 4);  // 输出"bcde"

Explanation: Since Chinese characters occupy 2 bytes, "bcdef" can be obtained by intercepting 4 characters starting from the first character.

Example 3:

$str = "abcdefg你好";
echo mb_substr($str, 4);   // 输出“g你好”

Explanation: If the third parameter (that is, the intercepted length) is omitted, it will be intercepted until the end of the string.

It should be noted that when the specified $start position exceeds the length of the string, the mb_substr() function will return an empty string. In addition, when the $length parameter is a negative number, the function will ignore it and intercept it to the end of the string.

When implementing a multi-language website, similar string interception tools will be used. In this case, it is more convenient to use the mb_substr() function, which can ensure correct processing of multi-byte characters without affecting the display effect of the page.

In general, the mb_substr() function is a very practical PHP string interception function that can correctly handle multi-byte encoded Chinese, Japanese and other characters, and is very convenient to use. For many developers who need to deal with multi-language websites or international projects, it is very necessary to be proficient in the mb_substr() function.

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