PHP deprecated functions, 8.1 to 8.5: the list, with replacements, for WordPress sites
Short answer
A deprecated function still works, but PHP writes a deprecation notice each time it’s called, and a later version usually removes it, which then stops the page. The ones WordPress plugins still call: PHP 8.1 deprecated strftime(), gmstrftime(), strptime(), date_sunrise(), date_sunset() and the mhash*() functions; 8.2 utf8_encode() and utf8_decode(); 8.3 get_class() without arguments and assert_options(); 8.4 lcg_value(), mysqli_ping(), mysqli_kill(), mysqli_refresh() and xml_set_object(); 8.5 curl_close(), curl_share_close(), imagedestroy(), finfo_close(), xml_parser_free() and two aliases. PHP 8.0 removed functions deprecated in 7.x, such as create_function() and each().
Deprecated, then removed
A deprecated function keeps working. PHP adds a notice every time it runs, so the code’s owner knows to change it. Here is strftime() on PHP 8.0 and on 8.1, which deprecated it:
wp-content/plugins/event-dates/event-dates.php
<?php
$timestamp = 1798675200; // 31 December 2026, 00:00 UTC
echo strftime('%Y-%m-%d', $timestamp), "\n";
2026-12-31Deprecated: Function strftime() is deprecated in /var/www/html/wp-content/plugins/event-dates/event-dates.php on line 3
2026-12-31Same result, plus a line in the log. When a later version removes a function, the first call stops the page with “Call to undefined function”: that is what happened to create_function() and each() in PHP 8.0. Deprecation notice or fatal error explains the difference for a site.
This list covers the deprecated functions that WordPress plugins are likely to call. php.net lists every deprecation of each version, including constants, arguments and rarer extensions (LDAP, Intl, ODBC…): see the links under each heading.
PHP 8.1
From php.net’s PHP 8.1 deprecations:
| Function | Use instead |
|---|---|
strftime(), gmstrftime() | date() / gmdate(), or IntlDateFormatter::format(); in WordPress, wp_date() |
strptime() | date_parse_from_format(), or IntlDateFormatter::parse() |
date_sunrise(), date_sunset() | date_sun_info() |
mhash(), mhash_keygen_s2k(), mhash_count(), mhash_get_block_size(), mhash_get_hash_name() | the hash_*() functions |
odbc_result_all() | no replacement |
mb_check_encoding() without arguments | pass the text to check |
More on the most common one: WordPress and PHP 8.1.
PHP 8.2
From php.net’s PHP 8.2 deprecations:
| Function | Use instead |
|---|---|
utf8_encode() | mb_convert_encoding( $text, 'UTF-8', 'ISO-8859-1' ) |
utf8_decode() | mb_convert_encoding( $text, 'ISO-8859-1', 'UTF-8' ) |
Both only ever converted from or to ISO-8859-1, which is often not what the code meant: utf8_encode() is deprecated explains the catch.
PHP 8.3
From php.net’s PHP 8.3 deprecations:
| Function | Use instead |
|---|---|
get_class(), get_parent_class() without arguments | self::class, parent::class, or get_class( $this ) |
assert_options() | ini_set() / ini_get() with the assert.* settings |
The fix for the first: “Calling get_class() without arguments is deprecated”.
PHP 8.4
From php.net’s PHP 8.4 deprecations:
| Function | Use instead |
|---|---|
lcg_value() | Random\Randomizer::getFloat() |
mysqli_ping() | nothing: the reconnect feature it served was removed in PHP 8.2 |
mysqli_kill() | the SQL command KILL |
mysqli_refresh() | the SQL command FLUSH |
xml_set_object() | pass the object with each handler, as [ $this, 'method' ] |
trigger_error() with E_USER_ERROR | throw an exception, or call exit() |
session_set_save_handler() with separate functions | a SessionHandlerInterface object |
A real finding for the first:
PHP 8.5
From php.net’s PHP 8.5 deprecations. Five of them were clean-up calls: php.net says the objects they close “are freed automatically”, so the call can simply go.
| Function | Use instead |
|---|---|
curl_close(), curl_share_close() | nothing: remove the call |
imagedestroy() | nothing: remove the call |
finfo_close() | nothing: remove the call |
xml_parser_free() | nothing: remove the call |
mysqli_execute() | mysqli_stmt_execute() |
socket_set_timeout() | stream_set_timeout() |
The most common one, with the fix for code that still supports PHP 7: curl_close() is deprecated.
Already removed: PHP 8.0
These were deprecated in PHP 7.2, 7.3 or 7.4, then removed in PHP 8.0. Every call is a fatal error:
| Function | Deprecated in | Use instead |
|---|---|---|
create_function() | 7.2 | an anonymous function: function () { … } |
each() | 7.2 | foreach |
read_exif_data() | 7.2 | exif_read_data() |
png2wbmp(), jpeg2wbmp(), gmp_random() | 7.2 | imagewbmp(), gmp_random_range() |
fgetss(), gzgetss(), image2wbmp() | 7.3 | strip_tags( fgets() ), imagewbmp() |
mbereg*(), mbsplit() and other mb* aliases | 7.3 | the same names with mb_: mb_ereg(), mb_split()… |
money_format() | 7.4 | NumberFormatter::formatCurrency() |
get_magic_quotes_gpc(), get_magic_quotes_runtime() | 7.4 | nothing: they always returned false |
hebrevc(), convert_cyr_string(), restore_include_path() | 7.4 | nl2br( hebrev() ), mb_convert_encoding(), ini_restore( 'include_path' ) |
ezmlm_hash() | 7.4 | no replacement |
The guides for the first two: create_function() and each(); and get_magic_quotes_gpc().
Find them in your plugins
Your error log shows a deprecated function only when the code that calls it runs: a function used in a monthly export stays invisible for weeks. A check that reads the code finds every call, before you upgrade.
CompatNav, a free plugin on wordpress.org, checks every plugin and theme for the functions on this page, among its 58 checks for PHP 8.0 to 8.5. It reports only what changes between the PHP version your site runs and the one you choose, each finding with the file, the line and the replacement, and skips calls already protected by a PHP version check or function_exists(). It runs on your own server and only reads files. Getting started shows the first scan.
Key takeaways
- Deprecated: still works, with a notice. Removed: a fatal error at the first call.
- PHP 8.0 removed functions deprecated in PHP 7.2 to 7.4, such as
create_function(),each()andmoney_format(). - Five of the PHP 8.5 deprecations are clean-up calls that no longer do anything: the call can simply go.
- Your error log shows a deprecated function only when the code runs; a code check finds every call before you upgrade.
- php.net’s pages list every deprecation, including rarer extensions; this list covers the functions plugins are likely to call.
Frequently asked questions
Do deprecated functions break my site?
Not while they’re only deprecated: the function runs and PHP writes a notice to the error log. They break when a later PHP version removes them; every call is then a fatal error.
When will PHP remove these functions?
php.net doesn’t give a date for each one. In the past, PHP removed deprecated functions in its next major version: PHP 8.0 removed the functions in the last table below, deprecated in PHP 7.2 to 7.4.
Is there a list of deprecated WordPress functions too?
Yes, WordPress deprecates its own functions too, with a different message that names a WordPress version. This page is about PHP’s own functions, which change with the PHP version.
Check your own site before you upgrade
CompatNav is a free WordPress plugin. It reads the code of your plugins and themes on your own server and tells you, in plain words, what will break and what will only show notices on the PHP version you choose. It never changes your code. It can’t see problems that only appear while code runs with real data, so a quick check of your site after the upgrade still matters.
Sources
- php.net: Deprecated features in PHP 8.1.x
- php.net: Deprecated features in PHP 8.2.x
- php.net: Deprecated features in PHP 8.3.x
- php.net: Deprecated features in PHP 8.4.x
- php.net: Deprecated features in PHP 8.5.x
- php.net: Backward incompatible changes in PHP 8.0.x
About the code examples: each output is the real output of the code shown, run with the official PHP builds, without a php.ini, with all errors reported and displayed. Only the file path was replaced by a neutral server path.