Just ran into this again in another project:

When using any of the iconv or mbstring functions which take a $charset or $encoding parameter in projects which have to be compatible with both PHP <= 5.5 as well as PHP 5.6, in most cases the results will only be the same if that (optional) parameter is set as otherwise the default encoding is used, as taken from the ini settings, and the default changed in PHP 5.6 (to utf-8).

This should be quite easily sniffable by searching for calls to these function and checking whether the parameter is set.

Refs:

• https://www.php.net/manual/en/book.iconv.php
• https://www.php.net/manual/en/book.mbstring.php

Related PHP migration guide entries:

Default character encoding ¶

default_charset is now used as the default character set for the htmlentities(), html_entity_decode() and htmlspecialchars() functions. Note that if the (now deprecated) iconv and mbstring encoding settings are set, they will take precedence over default_charset for iconv and mbstring functions, respectively.

The default value for this setting is UTF-8.

Ref: https://www.php.net/manual/en/migration56.new-features.php#migration56.new-features.default-encoding

iconv and mbstring encoding settings ¶

The iconv and mbstring configuration options related to encoding have been deprecated in favour of default_charset. The deprecated options are:

`iconv.input_encoding`
`iconv.output_encoding`
`iconv.internal_encoding`
`mbstring.http_input`
`mbstring.http_output`
`mbstring.internal_encoding`

Ref: https://www.php.net/manual/en/migration56.deprecated.php#migration56.deprecated.iconv-mbstring-encoding