Description:
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When using the chroot functionality with PHP-FPM and having the same path within the chroots of two different pools, the opcode cached code can get mixed up.

For example these two scripts get mixed up with opcode cache name:

Full path 1: /var/www/example1.com/var/www/htdocs/index.php
Chroot 1: /var/www/example1.com

Full path 2: /var/www/example2.com/var/www/htdocs/index.php
Chroot 2: /var/www/example2.com


Expected result:
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Update the documentation at https://secure.php.net/manual/en/install.fpm.configuration.php with a warning, something like this:

chroot string
Chroot to this directory at the start. This value must be defined as an absolute path. When this value is not set, chroot is not used.
>>> Be careful when using chroot with opcache! Since the opcache is shared between pools, the paths within the chroots must be unique per chroot, otherwise the opcache will lead to unexpected behavior. <<<

(Alternatively the FPM pool name could be added to the opcache key to avoid this behavior.)