PHP query UTF-8 encoded data in database

In today's Internet era, I believe that most websites are developed based on PHP language. However, PHP uses UTF-8 encoding by default starting from version 5.0. For developers who are not familiar with UTF-8 encoding, they may encounter some encoding problems, especially when processing database queries. In this article, I will teach you how to correctly query UTF-8 encoded data.

First of all, let us first understand what UTF-8 encoding is.

What is UTF-8 encoding?

UTF-8 is a variable-length character encoding and one of the implementations of Unicode. It encodes each Unicode character into a sequence of 1 to 4 bytes, and uses ASCII code for single-byte encoding of characters that consist only of letters of the alphabet. Due to its excellent versatility and compatibility, UTF-8 is widely used on the Internet.

How to query UTF-8 encoded data?

In PHP, the most common database operation is to query data. But if your data is UTF-8 encoded, you need to pay attention to the following aspects when querying:

1. You need to set the UTF-8 character set when connecting to the database

When connecting to the database, you need to set the character set of the database connection by specifying the parameter charset=UTF-8. For example:

$link = mysqli_connect("localhost", "my_user", "my_password", "my_database");
mysqli_set_charset($link, "utf8");

2. The SQL statement needs to specify the character set

When making a query, the character set needs to be specified in the SQL statement. For example:

$sql = "SELECT * FROM table_name WHERE name=?";
$stmt = mysqli_prepare($link, $sql);
mysqli_stmt_bind_param($stmt, "s", $name);
mysqli_stmt_execute($stmt);
mysqli_stmt_bind_result($stmt, $result);
mysqli_stmt_fetch($stmt);
mysqli_stmt_close($stmt);

In the above example, we use the mysqli_prepare() function to prepare the SQL statement, and use a question mark? in the SQL statement to represent the parameters that need to be bound. Then use the mysqli_stmt_bind_param() function to bind parameters. The first parameter of the function is the data type. Here we use "s" to represent the string type. Finally, the SQL statement is executed through the mysqli_stmt_execute() function, the result set is bound using the mysqli_stmt_bind_result() function, and the query results are obtained using the mysqli_stmt_fetch() function.

3. Check whether the data has been encoded in UTF-8

When querying, you need to check the obtained data to ensure that it is encoded in UTF-8 data. You can use the mb_detect_encoding() function in PHP to detect the encoding format of a string. For example:

$str = "需要检测的字符串";
if(mb_detect_encoding($str, "UTF-8", true) === false){
    $str = iconv("GB2312", "UTF-8", $str);
}

In the above example, we first used the mb_detect_encoding() function to detect the encoding format of the string $str. If the result is false, it means that it is not a UTF-8 encoded string. We You need to use the iconv() function to convert it to a UTF-8 encoded string.

Summary

Through the above steps, we can correctly query UTF-8 encoded data. Of course, the above is just a brief introduction to how to query UTF-8 encoded data. In actual projects, there may be more complex situations that need to be handled. However, as long as we master the basic methods and techniques, we will no longer have difficulties when dealing with Chinese encoding problems.

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