How Can I Ensure Consistent UTF-8 Encoding Throughout My Cross-Platform Web Application?

Cross-Platform “UTF-8 All the Way Through” Implementation

Background:

Ensuring consistent UTF-8 encoding throughout a web application can be a daunting task, especially when dealing with multiple system components. This article provides a comprehensive checklist and troubleshooting guide to help developers implement UTF-8 fully across all aspects of the application, from data storage to input handling.

Data Storage:

• Specify the utf8mb4 character set for tables and text columns in MySQL to store and retrieve values natively in UTF-8.
• If using older MySQL versions (< 5.5.3), use utf8 instead, which only supports a subset of Unicode characters.

Data Access:

In the application code, set the connection charset to utf8mb4:

• In PDO (PHP ≥ 5.3.6): $dbh = new PDO('mysql:charset=utf8mb4');
• In MySQLi: $mysqli->set_charset('utf8mb4'); or mysqli_set_charset($link, 'utf8mb4');
• In mysql (PHP ≥ 5.2.3): mysql_set_charset; if driver provides no mechanism, issue a query: SET NAMES 'utf8mb4'

Output:

• Set the correct HTTP header: Content-Type: text/html; charset=utf-8 using php.ini's default_charset or the header() function.
• Notify other systems of the encoding.
• Add JSON_UNESCAPED_UNICODE to json_encode() for JSON output.

Input:

• Verify request encoding using mb_check_encoding() to detect invalid UTF-8 submissions.

Other Code Considerations:

• Ensure all files are encoded in valid UTF-8.
• Utilize PHP's mbstring extension for safe UTF-8 string operations.
• Understand UTF-8 on a fundamental level to avoid encoding issues.

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