ServiceAccess (on github) is a AMFPHP plugin to secure access to PHP services easily. For instance with a minimal configuration, a method can be secured like this :

/**
* @rolesAllowed USER_WRITE, GROUP_WRITE
*
* The access to the function is granted to users that have the role USER_WRITE or GROUP_WRITE only.
*/
public function myFunction1() {...}

/**
* the next annotation can be removed since it is the default behavior
* @comityMode VETO
* @rolesAllowed USER_WRITE, GROUP_READ_ONLY
* @isCurrentUserLogin 1, login
* @checkMethod complexCheck
*
* The access is granted if
* the current user has the role USER_WRITE or GROUP_READ_ONLY
* OR
* the value of $userInfo->login is equal to the current user login
* OR
* the method 'complexCheck' returns true
*/
public function myFunction2($dataInfo, $userInfo) {...}

/**
* @comityMode ALL
* @rolesAllowed USER_WRITE, GROUP_READ_ONLY
* @isCurrentUserLogin 0, modifiedLogin
* @checkMethod simpleCheck
*
* The access is granted if
* the current user has the role USER_WRITE or GROUP_READ_ONLY
* AND
* the value of $dataInfo->modifiedLogin is equal to the current user login
* AND
* the method 'simpleCheck' returns true
*/
public function myFunction3($dataInfo, $userInfo) {...}

Check the documentation in the plugin package for more information on how to configure and customize ServiceAccess.