Magento 1.9.4 session error with PHP 7.2

[himanshutecstub]

Summary
Use magento 1.9.4.2 which is working fine with PHP 7.0 and MySql 5.6 with Cm_RedisSession
Now upgrade PHP version to 7.2.31 and MySql 5.7 with same code. It's slow down and got many session error as below (Redis Version : 6.0.5) and in website shown Out of memory error.

Examples
PHP Fatal error: Uncaught Error: __clone method called on non-object in /app/code/core/Mage/Core/Model/Session/Abstract.php:214
Warning: Unknown: Cannot call session save handler in a recursive manner in Unknown on line 0
Warning: Unknown: Failed to write session data using user defined save handler. (session.save_path: /var/lib/php/sessions) in Unknown on line 0
Warning: Cannot use a scalar value as an array in /app/code/core/Mage/Core/Model/Session/Abstract/Varien.php on line 446
Warning: Cannot use a scalar value as an array in /lib/Varien/Object.php on line 270

Also use latest Cm_Cache_Backend_Redis version for redis cache and also try to set zend.enable_gc = On.
How resolve that problem. is there any other settings required?

[seansan]

We are still seeing this error

2020-09-02T20:02:13+00:00 ERR (3): Warning: Unknown: Cannot call session save handler in a recursive manner in Unknown on line 0
2020-09-02T20:02:13+00:00 ERR (3): Warning: Unknown: Failed to write session data using user defined save handler. (session.save_path: /tmp) in Unknown on line 0

/tmp has rights drwxrwxrwt

To move forward on this

• could we better log the location "where" this goes wrong?
• can we improve logging to know "what" cannot be written?

At least then we are moving forward to identyfing a fix

Must be some config ... but we dont know which config

#156

https://stackoverflow.com/questions/34117651/php7-symfony-2-8-failed-to-write-session-data
zendframework/zend-session#77
laminas/laminas-session#6
https://stackoverflow.com/questions/46676474/warning-unknown-failed-to-write-session-data-using-user-defined-save-handler

[seansan]

Maybe add "Failed to write session data using user defined save handler" the error to the title

[seansan]

See #906