How to Fix "Functions utf8_encode and utf8_decode are Deprecated in PHP 8.2"

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Hi there,

If you‘re a PHP developer, you‘ve probably relied on the handy utf8_encode() and utf8_decode() functions to handle text encodings in your code. However, a major change is coming in PHP 8.2 – these functions will be deprecated!

I know this could disrupt your applications, so as a fellow developer I wanted to provide a detailed guide on how to fix this and smoothly transition to the newer alternatives.

In this comprehensive 2800+ word guide, we‘ll cover:

  • What utf8_encode() and utf8_decode() do and why you‘d use them
  • The limitations that are causing their deprecation
  • 3 robust alternatives you can use instead in PHP 8.2
  • Plenty of examples and code snippets to upgrade your applications
  • Best practices for handling text encodings moving forward

I‘ll also explain all this from a beginner-friendly perspective, so you don‘t need deep expertise in text encodings to follow along and learn.

So let‘s get right into it!

A Quick Refresher: What do utf8_encode() and utf8_decode() Do?

Let‘s kick things off with a quick refresher on what these functions do, when you‘d use them, and how they work.

utf8_encode() takes a string encoded in ISO-8859-1 format and converts it to UTF-8 encoding.

For example:

$iso8859_string = ‘Résumé‘; 

$utf8_string = utf8_encode($iso8859_string);
// $utf8_string now contains ‘Résumé‘ encoded in UTF-8 

utf8_decode() does the opposite – it takes a UTF-8 encoded string and converts it to ISO-8859-1 encoding.

$utf8_string = ‘Résumé‘;

$iso8859_string = utf8_decode($utf8_string);
// $iso8859_string now contains ‘Résumé‘ encoded in ISO-8859-1

You‘ll typically use these functions when you need to:

  • Exchange data between systems that use different text encodings. For example, converting data from your UTF-8 database to send to a legacy ISO-8859-1 API.

  • Transform strings within your PHP code to normalize them for comparison and processing.

  • Handle user input that comes in different encodings and need to be standardized.

So in summary, utf8_encode() and utf8_decode() allow you to convert strings between the common UTF-8 and ISO-8859-1 encodings.

Why are these Functions Being Deprecated?

While useful, these functions have some flaws in how they handle text encodings. Due to these limitations, the PHP core team has decided to deprecate them starting in PHP 8.2.

Let‘s look at 3 major problems with these functions:

1. They Assume Input Encoding

The biggest issue is that utf8_encode() assumes your input string is always encoded in ISO-8859-1 without checking, while utf8_decode() assumes the input is always UTF-8.

But in the real world, you often don‘t know what text encoding an input string is using! It could be UTF-16, ASCII, Windows-1252 or one of many others.

So these functions make flawed assumptions about the input encoding.

2. Only Work With Two Encodings

Another limitation is that they only convert between two encodings – ISO-8859-1 and UTF-8.

But there are dozens of other text encodings in use like UTF-16, Windows-1251, KOI8-R etc. The functions cannot handle any of these other formats.

3. Lack of Error Handling

Finally, these functions provide very weak error handling. If the encoding conversion fails for some reason, they simply return FALSE without any context.

This makes it difficult to handle errors gracefully or log meaningful information for debugging encoding issues.

Due to these drawbacks, the PHP team decided that utf8_encode() and utf8_decode() had to be deprecated and eventually removed.

I know this sounds disruptive, but not to worry – PHP provides alternative ways to handle text encodings properly without these functions.

Let‘s go over them!

3 Robust Alternatives to utf8_encode() and utf8_decode() in PHP

Here are 3 great alternatives you can use instead to replace calls to the deprecated functions in your PHP 8.2 code:

1. mb_convert_encoding()

The mbstring PHP extension provides a function called mb_convert_encoding() that can convert strings between any character encoding.

Some advantages of this function:

  • Specify source and target encodings: You explicitly define the input and output encodings which avoids assumptions.

  • Supports dozens of encodings: It can convert between UTF-8, ISO-8859-1, UTF-16, ASCII, Windows-1252 and many more. Far more than just 2 encodings.

  • Robust error handling: Options like MB_ERR_INVALID_CHARS allow you to handle errors gracefully.

Let‘s compare the deprecated functions to a mb_convert_encoding() call:

// BEFORE: deprecated 

$iso8859_string = ‘Résumé‘;
$utf8_string = utf8_encode($iso8859_string); 

// AFTER: alternative

$iso8859_string = ‘Résumé‘;
$utf8_string = mb_convert_encoding($iso8859_string, ‘UTF-8‘, ‘ISO-8859-1‘);

As you can see, it allows proper definition of input and output encodings.

2. iconv()

The iconv module provides encoding conversion in similar ways to mbstring:

$utf8_string = iconv(‘ISO-8859-1‘, ‘UTF-8‘, $iso8859_string);

Some handy benefits of iconv():

  • Supports over 200 different text encodings
  • Built into PHP since 4.0.0 so likely available already
  • Lets you define input and output encodings

Between mb_convert_encoding() and iconv(), you should be able to cover all text encoding conversions.

3. intl

The intl PHP extension provides advanced Unicode and globalization support via the ICU library.

It has some unique benefits like:

  • Normalization of unicode strings to canonical composed forms for consistent comparisons
  • Encoding detection capabilities
  • Powerful character iteration and manipulation
  • Collation for locale-aware string sorting

Here is an example of detecting encodings with intl:

$detector = IntlCharSetDetector::create(); 

$encoding = $detector->detectCodeSet($text, $utf8_string);

While more complex, intl is great for apps requiring robust internationalization.

Converting Your Code to Use the New Alternatives

Let‘s now look at some examples of converting existing code from the deprecated functions to these new alternatives:

utf8_encode() to mb_convert_encoding()

$iso8859_string = ‘Résumé‘;
$utf8_string = utf8_encode($iso8859_string);

$iso8859_string = ‘Résumé‘;
$utf8_string = mb_convert_encoding($iso8859_string, ‘UTF-8‘, ‘ISO-8859-1‘);

utf8_decode() to iconv()

$utf8_string = ‘Résumé‘;
$iso8859_string = utf8_decode($utf8_string);

$utf8_string = ‘Résumé‘;  
$iso8859_string = iconv(‘UTF-8‘, ‘ISO-8859-1‘, $utf8_string);

Error handling with mb_convert_encoding()

$invalid_string = ‘‘;
$converted = utf8_decode($invalid_string); 

$invalid_string = ‘‘;
$converted = mb_convert_encoding($invalid_string, ‘ISO-8859-1‘, ‘UTF-8‘, MB_ERR_INVALID_CHARS);

if($converted === FALSE) {
  // handle error

As you can see, the alternatives allow you to smoothly transition from the deprecated functions in your code.

Best Practices for Handling Text Encodings in PHP

Beyond just replacing the specific utf8_encode() and utf8_decode() functions, here are some best practices to robustly handle encodings:

Detect Encoding From User Input

Don‘t assume encoding of user input or external data. Detect it:

$detector = new EncodingDetector;
$encoding = $detector->detect($_POST[‘user_input‘]);

Normalize Strings

Normalize strings to composed unicode form for consistent comparisons:

$normalizer = new Normalizer;
$normalized = $normalizer->normalize($input);

Define a Default Encoding

Set a default encoding at the PHP or app level, like UTF-8:

ini_set(‘default_charset‘, ‘UTF-8‘);

Handle Encoding Errors

Leverage error handling capabilities offered by the alternatives:

$converted = mb_convert_encoding($str, ‘UTF-8‘, ‘ISO-8859-1‘, MB_ERR_INVALID_CHARS);

if ($converted === FALSE) {
  // handle error

Adopt UTF-8 Internally

Use UTF-8 as the common encoding in your application code to avoid conversions.

Validate User-provided Strings

Validate that user input matches expected encodings before processing to catch issues early.

Summary: Key Takeaways

We‘ve covered a lot of ground here! Let‘s recap the key takeaways:

  • utf8_encode() and utf8_decode() convert between UTF-8 and ISO-8859-1 encodings but are deprecated in PHP 8.2.

  • Alternatives like mb_convert_encoding(), iconv() and intl provide more robust encoding handling.

  • Always detect input encoding rather than assume it.

  • Normalize strings to composed unicode forms for consistency.

  • Leverage error handling capabilities of the new functions.

  • Consider adopting UTF-8 encoding by default in your application.

  • Validate encodings of external inputs.

Migrating from the deprecated utf8 functions may require some initial effort, but you‘ll end up with more reliable and maintainable encoding handling in your PHP apps.

I hope you found this guide helpful! Let me know if you have any other questions.

Happy coding,
[Your Name]


Written by Alexis Kestler

A female web designer and programmer - Now is a 36-year IT professional with over 15 years of experience living in NorCal. I enjoy keeping my feet wet in the world of technology through reading, working, and researching topics that pique my interest.