This is a quick checklist what I've used to make a PHP 5.6 to PHP 7.4 Migration

Migrating a PHP 5 App to PHP 7 (Rundown of PHP 7 Features) - Part 2

☐ mysql_connect and mysql_ related stuffs -> Change it to mysqli and OOP ☐ global $$ Not supported. You can "hack" using global ${$varname} ☐ Syntax Meaning Changes // old meaning // new meaning ☐ $$foo['bar']['baz'] ${$foo['bar']['baz']} ($$foo)['bar']['baz'] ☐ $foo->$bar['baz'] $foo->{$bar['baz']} ($foo->$bar)['baz'] ☐ $foo->$bar'baz' $foo->{$bar['baz']}() ($foo->$bar)'baz' ☐ Foo::$bar'baz' Foo::{$bar['baz']}() (Foo::$bar)'baz' ☐ ASP Short Tags Removed <% %> ☐ PHP Script tag <script language="php"></script> Removed ☐ set_exception_handler is not guaranteed ☐ password_hash Removed SALT Option ☐ capture_session_meta SSL context option has been deprecated. use stream_get_meta_data() to get SSL metadata. ☐ ldap_sort DEPRECATED with no replacement ☐ list() can no longer unpack string variables. str_split() should be used when performing this form of operation. ☐ HTTP_RAW_POST_DATA Removed ☐ Switch statements with multiple Default blocks isn't supported anymore ☐ Functions can not have multiple parameters with the same name. function slap($hand, $hand, $strength) ☐ Static calls made on non-static methods isn't allowed anymore ☐ class constructor now should be construct instead of className() ☐ **foreach with pointer doens't modify the array content foreach($arr as &$item) ☐ call_user_method() e call_user_method_array() REMOVED **☐ ereg functions REMOVED **☐ mcrypt_generic_end REMOVED **☐ mssql REMOVED ☐ datefmt_set_timezone_id() and IntlDateFormatter::setTimeZoneID() REMOVED ☐ set_magic_quotes_runtime & magic_quotes_runtime REMOVED ☐ set_socket_blocking REMOVED ☐ imagepsxxxxx function ☐ =& new (New instance as reference) REMOVED ☐ The e pattern modifier has been deprecated for the mb_ereg_replace() and mb_eregi_replace() functions. ☐ Continue Targeting Switch issues Warning

PHP 7.0 Migration Docs

PHP: Recursos depreciados no PHP 7.0.x - Manual

PHP 7.1 Migration Docs

PHP: Mudanças incompatíveis com versões anteriores - Manual

PHP: Deprecated features in PHP 7.1.x - Manual

PHP 7.2 Migration Docs

PHP: Backward incompatible changes - Manual

PHP: Recursos depreciados na versão PHP 7.2.x - Manual

PHP 7.3 Migration Docs

PHP: Backward incompatible changes - Manual

PHP: Deprecated Features - Manual

PHP 7.4 Migration Docs

PHP: Backward Incompatible Changes - Manual

PHP: Recursos depreciados - Manual

PHP: Alterações incompatíveis com versões anteriores - Manual