Solution to PHP mb_substr function not executing

PHP is a popular server-side scripting language commonly used to develop web applications. In PHP, the mb_substr() function is used to return a part of a string and intercept the string by specifying the position and length of the characters. However, in some cases, you may encounter the problem that the mb_substr() function is not executed. This article describes solutions to this common problem and provides specific code examples.

Problem description: When using the mb_substr() function to intercept a string, sometimes the function is not executed, resulting in the expected result not being obtained. This may be due to character encoding issues, especially when multi-byte characters are involved (such as Chinese, Japanese, etc.).

Solution: To solve this problem, you can set the correct character encoding before calling the mb_substr() function and ensure that the mbstring extension has been loaded. The following are specific solutions and code examples:

1. First, set the correct character encoding in the PHP code. You can use the mb_internal_encoding() function to set the default character encoding. For example, to set the character encoding to UTF-8, you would do this:

mb_internal_encoding('UTF-8');

2. Make sure the mbstring extension is loaded. The mbstring extension can be enabled in the php.ini configuration file or at runtime using the extension_loaded() function to check whether the mbstring extension has been loaded. If it is not loaded, it can be loaded by:

if (!extension_loaded('mbstring')) {
    dl('mbstring.so'); // 或者在Windows系统中使用：dl('php_mbstring.dll');
}

3. Make sure to use the mb_substr() function correctly. When calling the mb_substr() function, you need to pass in the correct parameters, including the string to be intercepted, the starting position and the length. The sample code is as follows:

$str = "这是一个测试字符串";
$start = 0; // 起始位置
$length = 5; // 需要截取的长度
$substring = mb_substr($str, $start, $length);

echo $substring; // 输出：这是一

Through the above three steps, you can solve the problem that the PHP mb_substr() function is not executed. Make sure to set the character encoding correctly, load the mbstring extension, and use the mb_substr() function correctly to intercept the string smoothly and get the expected results.

Summary: In PHP development, when the mb_substr() function is not executed, it is usually caused by character encoding problems. By correctly setting the character encoding, loading the mbstring extension, and correctly using the mb_substr() function, you can avoid this problem and perform string interception operations smoothly. I hope the above solutions and code examples can help PHP developers solve this type of problem.

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