Validate a package-style dependency. Validation is performed in this sequence:
If the dependency package provides an extension through the <providesextension>
tag, then see if it passes the extension validation test first and return if so.
If the list of packages to be installed contains a match for the dependency, use that
to validate the dependency and return.
If the dependency package is already installed, make sure the installed version
passes the conditions.
At this point, the dependency has failed. If the dependency is required,
return a PEAR_Error containing the failure error message, otherwise return
an array containing the error message.
Parameter
array
$dep
dependency array as defined by package.xml 2.0
boolean
$required
whether this is a required or optional dependency
array
$params
array of PEAR_Downloader_Package objects representing packages to be
downloaded that can be used to validate dependencies
boolean
$depv1
if TRUE, then deps on pear.php.net that fail will also check
against pecl.php.net packages to accomodate extensions that have
moved to pecl.php.net from pear.php.net
