How to limit the length of the returned string in php

PHP is a widely used server-side scripting language for creating dynamic web pages. In PHP, querying the database is a frequently used operation. When we query the database, we often encounter situations where the length of the returned string exceeds the limit. So in PHP, how to limit the length of the returned string?

1. substr() function

substr() function can return a substring of specified length from a string. For example, we can use the substr() function to limit the length of the returned string to 100:

$query = "SELECT * FROM table";
$result = mysqli_query($conn, $query);
$row = mysqli_fetch_assoc($result);
$limited_string = substr($row['content'], 0, 100);
echo $limited_string;

In the above code, we use the substr() function to limit the returned characters The string length is 100. In the substr() function, the first parameter is the string to be intercepted, the second parameter is the starting position of interception, and the third parameter is the length of interception.

2. mb_substr() function

If your string is a multi-byte character set (such as Chinese, Japanese, etc.), it is possible to use the substr() function Problems will arise. At this time, you can use the mb_substr() function. This function is a multibyte string function that can handle strings containing multibyte characters.

$query = "SELECT * FROM table";
$result = mysqli_query($conn, $query);
$row = mysqli_fetch_assoc($result);
$limited_string = mb_substr($row['content'], 0, 100, 'utf-8');
echo $limited_string;

In the above code, we use the mb_substr() function to limit the length of the returned string to 100. In the mb_substr() function, the first parameter is the string to be intercepted, the second parameter is the starting position of interception, the third parameter is the length of interception, and the fourth parameter is the character set .

3. Limit the return length in the database

In addition to limiting the length of the returned string in PHP, we can also set a limit on the return length in the database. In this way, when querying, the database will automatically return the length we need.

In the MySQL database, we can use the SUBSTRING() function to intercept strings. For example, we can use the following SQL statement to limit the length of the returned string to 100:

SELECT SUBSTRING(content, 1, 100) FROM table;

In the above SQL statement, the first parameter of the SUBSTRING() function is to The intercepted string, the second parameter is the starting position of interception, and the third parameter is the length of interception.

4. Summary

In PHP, the query return string length limit can be implemented using the substr() function or the mb_substr() function. . If your string is a multi-byte character set, it is recommended to use the mb_substr() function to limit the return length. If you want to set a limit on the return length in the database, you can use the SUBSTRING() function to achieve this.

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