Float addition/division issues

[AlexWinder]

Hello,

We have found an issue with our PHP Docker environment since an update has been pushed for the latest version of PHP 8.4.

We are using the php:8.4-fpm-bookworm base image.

We have the following PHP code:

[
            $this->north,
            $this->south,
            $this->east,
            $this->west,
            ($this->east + $this->west),
            ($this->east + $this->west) / 2,
            ($this->east + $this->west) / 2.0
]

Where this doesn't return consistently, sometimes we get this output, which is correct:

[
        38.924993216059,
        38.907006783941,
        1.4595583969657,
        1.4364416030343,
        2.896,
        1.448,
        1.448
]

Other times we get this output, which is breaking division:

[
        38.924993216059,
        38.907006783941,
        1.4595583969657,
        1.4364416030343,
        1.369313176327556e-309,
        6.8465658816378e-310,
        6.8465658816378e-310
]

The output is not consistent and sometimes returns the correct output, sometimes not.

This was highlighted in our automation tests, and with no changes to our underlying code. If we make use of the php:8.4.7-fpm-bookworm then the output is consistent and is correct. This appears to have been introduced with the recent update.

[AlexWinder]

We've found that disabling OpCache in our Dockerfile has caused the results to be consistent and correct all the time.

We disabled with the following:

RUN sed -i '/^;*opcache.enable\s*=.*/d' /usr/local/etc/php/php.ini && \
    echo "opcache.enable=0" >> /usr/local/etc/php/php.ini
RUN sed -i '/^;*opcache.enable_cli\s*=.*/d' /usr/local/etc/php/php.ini && \
    echo "opcache.enable_cli=0" >> /usr/local/etc/php/php.ini

[tianon]

Since this is filed more appropriately and being discussed upstream at php/php-src#18947, I'm going to go ahead and close this in favor of that ❤️