Installer fails PHP versions prior to 5.2.1

The CiviCRM installer fails attempts to install on PHP 5.2.0.

It does not appear that CiviCRM v2.1 uses any PHP 5.2.1 specific functions - http://nz.php.net/manual/en/migration52.functions.php - the new functions in 5.2.1 were ming/swf methods, stream_socket_shutdown() and sys_get_temp_dir()

The 5.2.1 requirement came in at r15437 - http://fisheye.civicrm.org/browse/~raw,r=15437/CiviCRM/trunk/install/index.php

This issue has been raised at http://forum.civicrm.org/index.php/topic,5860.0.html and http://forum.civicrm.org/index.php/topic,4430.0.html

The issue appears to have prevented some people from upgrading (Debian stable is 5.2.0 currently) and has caused other sites to upgrade entire servers based on the apparently mistaken impression that 5.2.1 is required to run CiviCRM 2.1.

In the earlier thread lobo suggested changing the version requirement back to 5.2.0.

5.2.0 is required because array_fill_keys is used - that appears to be the only 5.2.x series specific function.

I tested for 5.2.x series functions using,

ack "(array_fill_keys|error_get_last|image_type_to_extension|memory_get_peak_usage|sys_get_temp_dir|timezone_abbreviations_list|timezone_identifiers_list|timezone_name_from_abbr|stream_socket_shutdown|mb_stripos|mb_stristr|mb_strrchr|mb_strrichr|mb_strripos|mb_strstr|openssl_csr_get_public_key|openssl_csr_get_subject|openssl_pkey_get_details|spl_object_hash|preg_last_error|pg_field_table|posix_initgroups|gmp_nextprime|xmlwriter_full_end_element|xmlwriter_write_raw|xmlwriter_start_dtd_entity|xmlwriter_end_dtd_entity|xmlwriter_write_dtd_entity)" .