boolean PEAR_Info::packageInstalled ( 
    string $name
     , string $version
      = null
    
     , string $channel
      = null
    
     , string $user_file
      = ''
    
     , string $system_file
      = ''
    
   )
Simple function to check if a package is installed under user or system PEAR installation. Minimal version and channel info are supported.
$name
     Package name
$version
     (optional) The minimal version that should be installed
$channel
     (optional) The package channel distribution
$user_file
     (optional) file to read PEAR user-defined options from
$system_file
     (optional) file to read PEAR system-wide defaults from
since version 1.6.0 (2005-01-03)
throws no exceptions thrown
This function should be called statically.
<?php
require_once 'PEAR/Info.php';
$res = PEAR_Info::packageInstalled('Role_Web', '1.1.0', 'pearified');
if ($res) {
    print "Package pearified/Role_Web 1.1.0 or greater is installed \n";
} else {
    print "Package pearified/Role_Web is not yet installed \n";
}
$res = PEAR_Info::packageInstalled('PEAR_PackageFileManager');
if ($res) {
    print "Package pear/PEAR_PackageFileManager is installed \n";
} else {
    print "Package pear/PEAR_PackageFileManager is not yet installed \n";
}
?>