PHP 7.0 and MySQL start-up error “undefined symbol: mysqlnd_allocator in Unknown”

Question

Getting this warning on a custom-compiled version of PHP7, even when running php -v.

Tried all solutions posted. What could cause this?

Answer 1

(Posted on behalf of the OP).

Commands performed in order; I removed MySQL and PHP completely from system then:

sudo apt-get update
sudo apt-get install php7.0
sudo apt-get install php7.0-mysql

This seems to have fixed the error. Uuuugh.

Answer 2

Sometimes there is an issue with not loaded correctly extensions in the php.ini file. I had similar error and it start working only after I have added these extensions before pdo_mysql to the php.ini:

extension=mysqlnd    
extension=pdo
extension=pdo_mysql

And it finally worked!

However it shows warnings that mysqlnd, PDO and pdo_mysql was loaded before, it means that pdo_mysql already enabled and can be commented out at all. For further info please check PHP Warning: Module already loaded in Unknown on line 0

Answer 3

I found that I had

extension=pdo_mysql

uncommented in my php.ini file and this was causing the problem. Libraries are loaded by the files in the /etc/php/7.4/cli/conf.d/ file on my system and don't need to be loaded by uncommenting lines in the php.ini file.