printf-esque log method

Logging.php

<?php

trait Logging {
    /**
     * Write a log message.
     *
     * Write a log message to $this->_logCallback, $this->_logFile and/or
     * syslog.
     * Parameters are as for {@link http://php.net/sprintf sprintf}, except 
     * that a syslog priority (LOG_EMERG to LOG_DEBUG; see http://php.net/syslog) 
     * can be supplied as the first parameter.
     *
     * @author Craig Anderson <[email protected]>
     * @link https://gist.github.com/1849563
     */
    protected function _log() {
        if(is_callable($this->_logCallback) || $this->_logFile || $this->_logToSyslog) {
            $args = func_get_args();
            // If present, record priority, then remove it from arguments.
            $priority = $this->_defaultPriority;
            if(count($args) > 1 && is_numeric($args[0]) && $args[0] >= LOG_EMERG && $args[0] <= LOG_DEBUG) {
                $priority = (int)array_shift($args);
            }
            // Pass remaining arguments through sprintf
            if(count($args) == 1) {
                $message = $args[0];
            }
            else {
                // TODO: Escape extra '%' characters in the format?
                $message = call_user_func_array("sprintf", $args);
            }
            // Only show message if priority is less than or equal to the maximum priority
            if ($priority <= $this->_maximumPriority) {
                // Pass to log callback
                if(is_callable($this->_logCallback)) {
                    if(call_user_func($this->_logCallback, $message) === false) {
                        throw new RuntimeException("Couldn't call logging callback");
                    }
                }
                // Write to log file
                if($this->_logFile) {
                    if(!preg_match('/\n$/', $message)) {
                        $message .= "\n";
                    }
                    if(file_put_contents($this->_logFile, $message, FILE_APPEND) === false) {
                        if(!is_file($this->_logFile)) {
                            throw new RuntimeException("Couldn't create log file");
                        }
                        else {
                            throw new RuntimeException("Couldn't write to existing log file");
                        }
                    }
                }
                // Send to syslog
                if($this->_logToSyslog) {
                    if(is_null($this->_syslogIdentity)) {
                        $this->_syslogIdentity = get_class($this);
                    }
                    if(is_null($this->_syslogOptions)) {
                        $this->_syslogOptions = LOG_NDELAY | LOG_PID;
                    }
                    if(is_null($this->_syslogFacility)) {
                        $this->_syslogFacility = LOG_USER;
                    }
                    try {
                        if(!openlog($this->_syslogIdentity, $this->_syslogOptions, $this->_syslogFacility)) {
                            throw new RuntimeException("Call to openlog failed");
                        }
                        if(!syslog($priority, $message)) {
                            throw new RuntimeException("Call to syslog failed");
                        }
                        if(!closelog()) {
                            throw new RuntimeException("Call to closelog failed");
                        }
                    }
                    catch(Exception $e) {
                        @closelog();
                        throw $e;
                    }
                }
            }
        }
    }

    /**
     * Where to write log messages.
     */
    protected $_logCallback = null;
    protected $_logFile = "php://output";

    /**
     * Default and maximum priority.
     * Note that priorities run the opposite way to the way you might expect. Emergencies are very low, debug messages
     * are very high. See http://php.net/syslog for a list of priorities.
     */
    protected $_defaultPriority = LOG_INFO;
    protected $_maximumPriority = LOG_DEBUG;

    /**
     * Syslog settings.
     */
    protected $_logToSyslog = false;
    protected $_syslogIdentity = null; // If null, it'll be set to the result of get_class($this)
    protected $_syslogOptions = null;
    protected $_syslogFacility = null;
}