Amazon Lambda invocation error

I need to call my Amazon Lambda function, from php, but I am getting strange rights error when I have AWSLambdaFullAccess rights. My code:

$client = LambdaClient::factory(array(
'key' => 'AKI...G',
'secret' => 'VXD...YOse',
'region' => 'us-west-2'
));
$result = $client->invokeAsync(array(
'FunctionName' => 'arn:aws:lambda:us-west-2:180...52:function:fe...st',
'InvokeArgs' => json_encode($array),
));

This is the error:

User: arn:aws:iam::69...67:user/developer is not authorized to 
perform: lambda:InvokeFunction on resource: 
arn:aws:lambda:us-west-2:180...52:function:fe...st

Any ideas? Thanks