Apache Reference Manual (3)_PHP Tutorial

ContentDigest directive
Syntax: ContentDigest on|off
Default: ContentDigest off
Context: server config, virtual host, directory, .htaccess
Override: Options
Status: experimental
Compatibility: ContentDigest is only available in Apache 1.1 and later
This directive enables the generation of Content-MD5 headers as defined in RFC1864 respectively RFC2068.
MD5 is an algorithm for computing a "message digest" (sometimes called "fingerprint") of arbitrary-length data, with a high degree of confidence that any alterations in the data will be reflected in alterations in the message digest.
The Content-MD5 header provides an end-to-end message integrity check (MIC) of the entity-body. A proxy or client may check this header for detecting accidental modification of the entity-body in transit. Example header:
     Content-MD5: AuLb7Dp1rqtRtxz2m9kRpA==
Note that this can cause performance problems on your server since the message digest is computed on every request (the values are not cached).
Content-MD5 is only sent for documents served by the core, and not by any module. For example, SSI documents, output from CGI scripts, and byte range responses do not have this header.
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CoreDumpDirectory directive
Syntax: CoreDumpDirectory directory
Default: the same location as ServerRoot
Context: server config
Status: core
This controls the directory to which Apache attempts to switch before dumping core. The default is in the ServerRoot directory, however since this should not be writable by the user the server runs as, core dumps won't normally get written. If you want a core dump for debugging, you can use this directive to place it in a different location.
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DefaultType directive