Most people are running older versions of the Ioncube loaders, and PHP 5.5 supported builds of Blesta are not backwards compatible with these legacy loaders. Additionally, Blesta must be encoded for PHP 5.3 or 5.4 support in order to work with PHP 5.5, per this thread on Ioncube's forums, quoted below --
But, the minimum requirement for Blesta is PHP 5.1.3, so we have been releasing builds that are compatible for the majority (PHP 5.1.3 through 5.4.x), but not compatible with PHP 5.5. Adoption rates for PHP 5.5 are increasing, and we recognize the need to support it.
At this time, due to Ioncube's limitations, we would be required to have 2 separate builds in order to support PHP 5.1.3-5.4.x and PHP 5.5.
We are releasing this hotfix to allow PHP 5.5 support for Blesta 3.1.3. The zip contains only the 3 files we encode, to protect licensing. If you are not running Blesta 3.1.3 DO NOT apply the hotfix.
blesta-3.1.3-php-5.5-hotfix.zip
If you are doing a fresh install, first download blesta-3.1.3.zip and overwrite the files in 3.1.3 from the hotfix above before attempting the installation.
If you are planning to upgrade your existing server to PHP 5.5 and have Blesta 3.1.3 installed, overwrite the files in the hotfix above after you upgrade your PHP.