added setLogger() method to configure logging

Author: skoerfgen

README.md

@@ -1,7 +1,7 @@
 # ACMECert
 
 PHP client library for [Let's Encrypt](https://letsencrypt.org/) and other [ACME v2 - RFC 8555](https://tools.ietf.org/html/rfc8555) compatible Certificate Authorities.  
-Version: 3.2.2
+Version: 3.3.0
 
 ## Description
 
@@ -324,14 +324,23 @@ if ($days>30) { // renew 30 days before expiry
 
 ## Logging
 
-ACMECert logs its actions using `error_log`, which logs messages to stderr per default in PHP CLI so it is easy to log to a file instead:
+By default ACMECert logs its actions using `error_log` which logs messages to stderr in PHP CLI so it is easy to log to a file instead:
 ```php
 error_reporting(E_ALL);
 ini_set('log_errors',1);
 ini_set('error_log',dirname(__FILE__).'/ACMECert.log');
 ```
 
-
+> To disable the default logging, you can use [`setLogger`](#acmecertsetlog), Exceptions are nevertheless thrown:
+```php
+$ac->setLogger(false);
+```
+> Or you can you set it to a custom callback function:
+```php
+$ac->setLogger(function($txt){
+	echo 'Log Message: '.$txt."\n";
+});
+```
 ## ACME_Exception
 
 If the ACME-Server responded with an error message an `\skoerfgen\ACMECert\ACME_Exception` is thrown. (ACME_Exception extends Exception)
@@ -883,6 +892,29 @@ public array ACMECert::getTermsURL()
 
 ---
 
+### ACMECert::setLogger
+
+Turn on/off logging to stderr using `error_log` or provide a custom callback function.
+```php
+public void ACMECert::setLogger( bool|callable $value = TRUE )
+```
+###### Parameters
+> **`value`**
+>
+> - If `TRUE`, logging to stderr using `error_log` is enabled. (default)
+> - If `FALSE`, logging is disabled.
+> - If a callback function is provided, the function gets called with the log message as first argument:
+> ```php
+> void callback( string $txt )
+> ```
+> see [Logging](#logging)
+###### Return Values
+> No value is returned.
+###### Errors/Exceptions
+> Throws an `Exception` if the value provided is not boolean or a callable function.
+
+---
+
 > MIT License
 >
 > Copyright (c) 2018 Stefan Körfgen

composer.json

@@ -1,6 +1,6 @@
 {
 	"name": "skoerfgen/acmecert",
-	"version": "3.2.2",
+	"version": "3.3.0",
 	"description": "PHP client library for Let's Encrypt and other ACME v2 - RFC 8555 compatible Certificate Authorities",
 	"license": "MIT",
 	"authors": [

src/ACMEv2.php

@@ -37,7 +37,7 @@ class ACMEv2 { // Communication with Let's Encrypt via ACME v2 protocol
 		$directories=array(
 			'live'=>'https://acme-v02.api.letsencrypt.org/directory',
 			'staging'=>'https://acme-staging-v02.api.letsencrypt.org/directory'
-		),$ch=null,$bits,$sha_bits,$directory,$resources,$jwk_header,$kid_header,$account_key,$thumbprint,$nonce=null;
+		),$ch=null,$logger=true,$bits,$sha_bits,$directory,$resources,$jwk_header,$kid_header,$account_key,$thumbprint,$nonce=null;
 	private $delay_until=null;
 
 	public function __construct($live=true){
@@ -113,8 +113,31 @@ public function getAccountID(){
 		return $this->kid_header['kid'];
 	}
 
+	public function setLogger($value=true){
+		switch(true){
+			case is_bool($value):
+			break;
+			case is_callable($value):
+			break;
+			default:
+				throw new Exception('setLogger: invalid value provided');
+			break;
+		}
+		$this->logger=$value;
+	}
+
 	public function log($txt){
-		error_log($txt);
+		switch(true){
+			case $this->logger===true:
+				error_log($txt);
+			break;
+			case $this->logger===false:
+			break;
+			default:
+				$fn=$this->logger;
+				$fn($txt);
+			break;
+		}
 	}
 
 	protected function create_ACME_Exception($type,$detail,$subproblems=array()){
@@ -286,7 +309,7 @@ private function http_request($url,$data=null){
 		}
 
 		$method=$data===false?'HEAD':($data===null?'GET':'POST');
-		$user_agent='ACMECert v3.2.2 (+https://github.com/skoerfgen/ACMECert)';
+		$user_agent='ACMECert v3.3.0 (+https://github.com/skoerfgen/ACMECert)';
 		$header=($data===null||$data===false)?array():array('Content-Type: application/jose+json');
 		if ($this->ch) {
 			$headers=array();