Having not enough memory can cause all kinds of problems, which don't necessarily have to lead to the "out of memory" error message. If you get the error message or any kind of weird non-tracable behaviour (page not found, blank screens, etc.) after the initial install, try raising the memory as explained below.

On some configurations, eZ publish 3 needs more than 8Mb internal memory, especially when loaded for the first time.

Please raise the memorylimit for php, i.e. set

php_admin_value memory_limit 20M

in the (virtual) server config or set

memory_limit 20M

directly in the PHP configuration file php.ini.

You can also try to set it in the PHP file start using the function

ini_set ( "memory_limit", "20M")

wich sets the value of the given configuration option. Returns the old value on success, FALSE on failure. The configuration option will keep this new value during the script's execution, and will be restored at the script's ending.

If your Webspace is able to handle ".htaccess" files then you could also set it by adding the following line

php_value memory_limit 20M

which avoid the need to include the previous instruction at the start of ALL PHP scripts.

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Note #1. Not all the available options can be changed using ini_set(). This can be changed/set (as of PHP 4.2.0) at level PHP_INI_ALL (Entry can be set anywhere).
Get more detailed info about ini_set() at http://www.php.net/manual/en/function.ini-set.php

Note #2. This can also be caused by a PHP acellerator not clearing memory.