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PHP convert_cyr_string Function – Complete Guide

The PHP convert_cyr_string() function is used to convert a string between different Cyrillic character encodings.

This function is mainly useful when working with Russian, Ukrainian, or other Cyrillic-based languages in legacy systems.

In this guide, you’ll learn how it works, syntax, examples, and best practices in a simple and beginner-friendly way.

What is convert_cyr_string() in PHP?

The convert_cyr_string() function converts text from one Cyrillic encoding to another.

Simple idea:
Convert text → from one encoding → to another encoding

Why is it Important?

Different systems use different encodings like:

  • Windows-1251
  • KOI8-R
  • ISO-8859-5

If encodings don’t match, text may look like:
Привет instead of Привет

This function helps fix such issues.

Syntax of convert_cyr_string()

string convert_cyr_string(string $str, string $from, string $to)

Parameters Explained

ParameterDescription
$strInput string
$fromSource encoding
$toTarget encoding

Encoding Codes

CodeEncoding
kKOI8-R
wWindows-1251
iISO-8859-5
ax-cp866
dx-cp866
mx-mac-cyrillic

Basic Example

<?php
$text = "Привет"; // Cyrillic text

$converted = convert_cyr_string($text, 'w', 'k');

echo $converted;
?>

Explanation

  • 'w' = Windows-1251
  • 'k' = KOI8-R
  • Converts text between encodings

👉 Output may not display correctly unless encoding matches your browser.

Real-World Use Cases

Fixing Garbled Text

<?php
$text = "Привет";
$fixed = convert_cyr_string($text, 'k', 'w');
?>

Working with Legacy Systems

Older applications may use different encodings.

$data = convert_cyr_string($input, 'i', 'w');

Data Migration

Convert database data:

$converted = convert_cyr_string($oldData, 'a', 'w');

Common Mistakes

Wrong Encoding Codes

❌ Wrong:

convert_cyr_string($text, ‘utf8’, ‘w’);

✔ Correct:

convert_cyr_string($text, ‘w’, ‘k’);
 

Using with UTF-8

 Important:
This function does NOT support UTF-8

Use iconv() or mb_convert_encoding() instead.

 Expecting Encryption

  • This is NOT encryption
  • It only converts encoding

Advanced Example

<?php
header("Content-Type: text/html; charset=windows-1251");

$text = "Привет мир";
$converted = convert_cyr_string($text, 'k', 'w');

echo $converted;
?>

Explanation

  • Sets correct browser encoding
  • Ensures proper display
  • Prevents garbled output

FAQs

What does convert_cyr_string() do?

It converts Cyrillic text between different encodings.

Does it support UTF-8?

No, it only supports specific Cyrillic encodings.

 Is this function still used?

Mostly in legacy systems.

What is the best alternative?

Use iconv() or mb_convert_encoding().

Why is my output unreadable?

Because encoding does not match browser or system.

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