TYPO3 Core

When the php5-zlib package is not installed (which is the default in some Linux distributions)), the following happens during the installation of the Typo3 Introduction Package:

SC_mod_tools_em_terconnection.decodeExchangeData() returns a string with the error message "Decoding Error: No decompressor available for compressed content. gzcompress()/gzuncompress() functions are not available!"

In tx_introduction_import_extension.importExtension() the string with this error message is stored in $extensionArray. There should error handling here like:
if (!is_array($extensionArray)) { ... process error ...}
but instead the next statement tries to access $extensionArray⁰['EM_CONF'] which leads to the error "PHP Fatal error: Cannot use string offset as an array in /.../typo3conf/ext/introduction/Classes/Import/Extension.php on line 103". This error message is only visible in the Apache error log and the user only gets a blank web page without any indication of an error.

I suggest to:

1. Add error handling to tx_introduction_import_extension.importExtension() to test whether decodeExchangeData() returns an array or an error message.

2. Add general error handling so that an error message is displayed when e.g. a fatal PHP error occurs during the installation of the Introduction Package.

3. Add a check for the availability of the gzcompress()/gzuncompress() functions (PHP ZLib package) to the "Basic Configuration" page of the Install Tool.

(issue imported from #M15780)