pear/log

PEAR Logging Framework

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1.14.4 2024-02-20 21:00 UTC

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MIT f1ce70cfc8ee30af93c313f4e6444a7abe6aea03

loglogging

This package is auto-updated.

Last update: 2024-07-20 21:58:03 UTC

README

User Documentation

Contents

1   Using Log Handlers

The Log package is implemented as a framework that supports the notion of backend-specific log handlers. The base logging object (defined by the Log class) is primarily an abstract interface to the currently configured handler.

A wide variety of handlers are distributed with the Log package, and, should none of them fit your application's needs, it's easy to write your own.

1.1   Creating a Log Object

There are three ways to create Log objects:

  • Using the Log::factory() method
  • Using the Log::singleton() method
  • Direct instantiation

1.1.1   The Factory Method

The Log::factory() method implements the Factory Pattern. It allows for the parameterized construction of concrete Log instances at runtime. The first parameter to the Log::factory() method indicates the name of the concrete handler to create. The rest of the parameters will be passed on to the handler's constructor (see Configuring a Handler below).

The new Log instance is returned by reference.

require_once 'Log.php';

$console = Log::factory('console', '', 'TEST');
$console->log('Logging to the console.');

$file = Log::factory('file', 'out.log', 'TEST');
$file->log('Logging to out.log.');

1.1.2   The Singleton Method

The Log::singleton() method implements the Singleton Pattern. The singleton pattern ensures that only a single instance of a given log type and configuration is ever created. This has two benefits: first, it prevents duplicate Log instances from being constructed, and, second, it gives all of your code access to the same Log instance. The latter is especially important when logging to files because only a single file handler will need to be managed.

The Log::singleton() method's parameters match the Log::factory() method. The new Log instance is returned by reference.

require_once 'Log.php';

/* Same construction parameters */
$a = Log::singleton('console', '', 'TEST');
$b = Log::singleton('console', '', 'TEST');

if ($a === $b) {
    echo '$a and $b point to the same Log instance.' . "\n";
}

/* Different construction parameters */
$c = Log::singleton('console', '', 'TEST1');
$d = Log::singleton('console', '', 'TEST2');

if ($c !== $d) {
    echo '$c and $d point to different Log instances.' . "\n";
}

1.1.3   Direct Instantiation

It is also possible to directly instantiate concrete Log handler instances. However, this method is not recommended because it creates a tighter coupling between your application code and the Log package than is necessary. Use of the factory method or the singleton method is preferred.

1.2   Configuring a Handler

A log handler's configuration is determined by the arguments used in its construction. Here's an overview of those parameters:

/* Using the factory method ... */
Log::factory($handler, $name, $ident, $conf, $maxLevel);

/* Using the singleton method ... */
Log::singleton($handler, $name, $ident, $conf, $maxLevel);

/* Using direct instantiation ... */
new Log_handler($name, $ident, $conf, $maxLevel);

1.3   Logging an Event

Events are logged using the log() method:

$logger->log('Message', PEAR_LOG_NOTICE);

The first argument contains the log event's message. Even though the event is always logged as a string, it is possible to pass an object to the log() method. If the object implements a getString() method, a toString() method or Zend Engine 2's special __toString() casting method, it will be used to determine the object's string representation. Otherwise, the serialized form of the object will be logged.

The second, optional argument specifies the log event's priority. See the Log Levels table for the complete list of priorities. The default priority is PEAR_LOG_INFO.

The log() method will return true if the event was successfully logged.

"Shortcut" methods are also available for logging an event at a specific log level. See the Log Levels table for the complete list.

1.4   Log Levels

This table is ordered by highest priority (PEAR_LOG_EMERG) to lowest priority (PEAR_LOG_DEBUG).

1.5   Log Level Masks

Defining a log level mask allows you to include and/or exclude specific levels of events from being logged. The $level construction parameter (see Configuring a Handler) uses this mechanism to exclude log events below a certain priority, and it's possible to define more complex masks once the Log object has been constructed.

Each priority has a specific mask associated with it. To compute a priority's mask, use the static Log::MASK() method:

$mask = Log::MASK(PEAR_LOG_INFO);

To compute the mask for all priorities up to, and including, a certain level, use the Log::MAX() static method:

$mask = Log::MAX(PEAR_LOG_INFO);

To compute the mask for all priorities greater than or equal to a certain level, use the Log::MIN() static method:

$mask = Log::MIN(PEAR_LOG_INFO);

The apply the mask, use the setMask() method:

$logger->setMask($mask);

Masks can be be combined using bitwise operations. To restrict logging to only those events marked as PEAR_LOG_NOTICE or PEAR_LOG_DEBUG:

$mask = Log::MASK(PEAR_LOG_NOTICE) | Log::MASK(PEAR_LOG_DEBUG);
$logger->setMask($mask);

For convenience, two special masks are predefined: PEAR_LOG_NONE and PEAR_LOG_ALL. PEAR_LOG_ALL is especially useful for excluding only specific priorities:

$mask = PEAR_LOG_ALL ^ Log::MASK(PEAR_LOG_NOTICE);
$logger->setMask($mask);

It is also possible to retrieve and modify a Log object's existing mask:

$mask = $logger->getMask() | Log::MASK(PEAR_LOG_INFO);
$logger->setMask($mask);

1.6   Log Line Format

Most log handlers support configurable line formats. The following is a list of special tokens that will be expanded at runtime with contextual information related to the log event. Each token has an alternate shorthand notation, as well.

1.7   Flushing Log Events

Some log handlers (such as the console handler) support explicit "buffering". When buffering is enabled, log events won't actually be written to the output stream until the handler is closed. Other handlers (such as the file handler) support implicit buffering because they use the operating system's IO routines, which may buffer the output.

It's possible to force these handlers to flush their output, however, by calling their flush() method:

$conf = ['buffering' => true];
$logger = Log::singleton('console', '', 'test', $conf);

for ($i = 0; $i < 10; $i++) {
    $logger->log('This event will be buffered.');
}

/* Flush all of the buffered log events. */
$logger->flush();

for ($i = 0; $i < 10; $i++) {
    $logger->log('This event will be buffered.');
}

/* Implicitly flush the buffered events on close. */
$logger->close();

At this time, the flush() method is only implemented by the console handler, the file handler, the Firebug handler, and the mail handler.

2   Standard Log Handlers

2.1   The Console Handler

The Console handler outputs log events directly to the console. It supports output buffering and configurable string formats.

2.1.1   Configuration

2.1.2   Example

$logger = Log::singleton('console', '', 'ident');
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.2   The Display Handler

The Display handler simply prints the log events back to the browser. It respects the error_prepend_string and error_append_string error handling values and is useful when logging from standard error handlers.

2.2.1   Configuration

2.2.2   Example

$conf = ['error_prepend' => '<font color="#ff0000"><tt>',
              'error_append'  => '</tt></font>'];
$logger = Log::singleton('display', '', '', $conf, PEAR_LOG_DEBUG);
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.3   The Error_Log Handler

The Error_Log handler sends log events to PHP's error_log() function.

2.3.1   Configuration

2.3.2   Error_Log Types

All of the available log types are detailed in the error_log() section of the PHP manual. For your convenience, the Log package also defines the following constants that can be used for the $name handler construction parameter.

2.3.3   Example

$logger = Log::singleton('error_log', PEAR_LOG_TYPE_SYSTEM, 'ident');
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.4   The File Handler

The File handler writes log events to a text file using configurable string formats.

2.4.1   Configuration

The file handler will only attempt to set the mode value if it was responsible for creating the file.

2.4.2   Example

$conf = ['mode' => 0600, 'timeFormat' => '%X %x'];
$logger = Log::singleton('file', 'out.log', 'ident', $conf);
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.5   The Firebug Handler

The Firebug handler outputs log events to the Firebug console. It supports output buffering and configurable string formats.

2.5.1   Configuration

2.5.2   Example

$logger = Log::singleton('firebug', '', 'ident');
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.6   The Mail Handler

The Mail handler aggregates a session's log events and sends them in the body of an email message using either the PEAR Mail package or PHP's native mail() function.

If an empty mailBackend value is specified, the mail() function will be used instead of the PEAR Mail package.

Multiple recipients can be specified by separating their email addresses with commas in the $name construction parameter.

2.6.1   Configuration

2.6.2   Example

$conf = ['subject' => 'Important Log Events'];
$logger = Log::singleton('mail', 'webmaster@example.com', 'ident', $conf);
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.7   The MDB2 Handler

The MDB2 handler is similar to the SQL (DB) handler, but instead of using the PEAR DB package, it uses the MDB2 database abstraction package.

2.7.1   Configuration

2.8   The Null Handler

The Null handler simply consumes log events (akin to sending them to /dev/null). Log level masks are respected, and the event will still be sent to any registered log observers.

2.8.1   Example

$logger = Log::singleton('null');
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.9   The SQL (DB) Handler

The SQL handler sends log events to a database using PEAR's DB abstraction layer.

Note: Due to the constraints of the default database schema, the SQL handler limits the length of the $ident string to sixteen (16) characters. This limit can be adjusted using the identLimit configuration parameter.

2.9.1   The Log Table

The default SQL table used by this handler looks like this:

CREATE TABLE log_table (
    id          INT NOT NULL,
    logtime     TIMESTAMP NOT NULL,
    ident       CHAR(16) NOT NULL,
    priority    INT NOT NULL,
    message     VARCHAR(200),
    PRIMARY KEY (id)
);

This is the "lowest common denominator" that should work across all SQL compliant database. You may want to make database- or site-specific changes to this schema to support your specific needs, however. For example, PostgreSQL users may prefer to use a TEXT type for the message field.

2.9.2   Configuration

The name of the database table to which the log entries will be written is specified using the $name construction parameter (see Configuring a Handler).

2.9.3   Examples

Using a Data Source Name to create a new database connection:

$conf = ['dsn' => 'pgsql://jon@localhost+unix/logs'];
$logger = Log::singleton('sql', 'log_table', 'ident', $conf);
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

Using an existing DB object:

require_once 'DB.php';
$db = &DB::connect('pgsql://jon@localhost+unix/logs');

$conf['db'] = $db;
$logger = Log::singleton('sql', 'log_table', 'ident', $conf);
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.10   The Sqlite Handler

The Sqlite handler sends log events to an Sqlite database using the native PHP sqlite functions.

It is faster than the SQL (DB) handler because requests are made directly to the database without using an abstraction layer. It is also interesting to note that Sqlite database files can be moved, copied, and deleted on your system just like any other files, which makes log management easier. Last but not least, using a database to log your events allows you to use SQL queries to create reports and statistics.

When using a database and logging a lot of events, it is recommended to split the database into smaller databases. This is allowed by Sqlite, and you can later use the Sqlite ATTACH statement to query your log database files globally.

If the database does not exist when the log is opened, sqlite will try to create it automatically. If the log table does not exist, it will also be automatically created. The table creation uses the following SQL request:

CREATE TABLE log_table (
    id          INTEGER PRIMARY KEY NOT NULL,
    logtime     NOT NULL,
    ident       CHAR(16) NOT NULL,
    priority    INT NOT NULL,
    message
);

2.10.1   Configuration

An already opened database connection can also be passed as parameter instead of the above configuration. In this case, closing the database connection is up to the user.

2.10.2   Examples

Using a configuration to create a new database connection:

$conf = ['filename' => 'log.db', 'mode' => 0666, 'persistent' => true];
$logger = Log::factory('sqlite', 'log_table', 'ident', $conf);
$logger->log('logging an event', PEAR_LOG_WARNING);

Using an existing connection:

$db = sqlite_open('log.db', 0666, $error);
$logger = Log::factory('sqlite', 'log_table', 'ident', $db);
$logger->log('logging an event', PEAR_LOG_WARNING);
sqlite_close($db);

2.11   The Syslog Handler

The Syslog handler sends log events to the system logging service (syslog on Unix-like environments or the Event Log on Windows systems). The events are sent using PHP's syslog() function.

2.11.1   Configuration

2.11.2   Facilities

2.11.3   Example

$logger = Log::singleton('syslog', LOG_LOCAL0, 'ident');
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

2.12   The Window Handler

The Window handler sends log events to a separate browser window. The original idea for this handler was inspired by Craig Davis' Zend.com article entitled "JavaScript Power PHP Debugging".

2.12.1   Configuration

Note: The Window handler may not work reliably when PHP's output buffering system is enabled.

2.12.2   Example

$conf = ['title' => 'Sample Log Output'];
$logger = Log::singleton('win', 'LogWindow', 'ident', $conf);
for ($i = 0; $i < 10; $i++) {
    $logger->log("Log entry $i");
}

3   Composite Handlers

It is often useful to log events to multiple handlers. The Log package provides a compositing system that marks this task trivial.

Start by creating the individual log handlers:

$console = Log::factory('console', '', 'TEST');
$file = Log::factory('file', 'out.log', 'TEST');

Then, construct a composite handler and add the individual handlers as children of the composite:

$composite = Log::singleton('composite');
$composite->addChild($console);
$composite->addChild($file);

The composite handler implements the standard Log interface so you can use it just like any of the other handlers:

$composite->log('This event will be logged to both handlers.');

Children can be removed from the composite when they're not longer needed:

$composite->removeChild($file);

4   Log Observers

Log observers provide an implementation of the observer pattern. In the content of the Log package, they provide a mechanism by which you can examine (i.e. observe) each event as it is logged. This allows the implementation of special behavior based on the contents of a log event. For example, the observer code could send an alert email if a log event contained the string PANIC.

Creating a log observer involves implementing a subclass of the Log_observer class. The subclass must override the base class's notify() method. This method is passed a hash containing the event's priority and event. The subclass's implementation is free to act upon this information in any way it likes.

Log observers are attached to Log instances via the attach() method:

$observer = Log_observer::factory('yourType');
$logger->attach($observer);

Observers can be detached using the detach() method:

$logger->detach($observer);

At this time, no concrete Log_observer implementations are distributed with the Log package.

5   Logging From Standard Error Handlers

5.1   Logging PHP Errors

PHP's default error handler can be overridden using the set_error_handler() function. The custom error handling function can use a global Log instance to log the PHP errors.

Note: Fatal PHP errors cannot be handled by a custom error handler at this time.

function errorHandler($code, $message, $file, $line)
{
    global $logger;

    /* Map the PHP error to a Log priority. */
    switch ($code) {
    case E_WARNING:
    case E_USER_WARNING:
        $priority = PEAR_LOG_WARNING;
        break;
    case E_NOTICE:
    case E_USER_NOTICE:
        $priority = PEAR_LOG_NOTICE;
        break;
    case E_ERROR:
    case E_USER_ERROR:
        $priority = PEAR_LOG_ERR;
        break;
    default:
        $priority = PEAR_LOG_INFO;
    }

    $logger->log($message . ' in ' . $file . ' at line ' . $line,
                 $priority);
}

set_error_handler('errorHandler');
trigger_error('This is an information log message.', E_USER_NOTICE);

5.2   Logging PHP Assertions

PHP allows user-defined assert() callback handlers. The assertion callback is configured using the assert_options() function.

function assertCallback($file, $line, $message)
{
    global $logger;

    $logger->log($message . ' in ' . $file . ' at line ' . $line,
                 PEAR_LOG_ALERT);
}

assert_options(ASSERT_CALLBACK, 'assertCallback');
assert(false);

5.3   Logging PHP Exceptions

PHP 5 and later support the concept of exceptions. A custom exception handler can be assigned using the set_exception_handler() function.

function exceptionHandler($exception)
{
    global $logger;

    $logger->log($exception->getMessage(), PEAR_LOG_ALERT);
}

set_exception_handler('exceptionHandler');
throw new Exception('Uncaught Exception');

5.4   Logging PEAR Errors

The Log package can be used with PEAR::setErrorHandling()'s PEAR_ERROR_CALLBACK mechanism by writing an error handling function that uses a global Log instance. Here's an example:

function errorHandler($error)
{
    global $logger;

    $message = $error->getMessage();

    if (!empty($error->backtrace[1]['file'])) {
        $message .= ' (' . $error->backtrace[1]['file'];
        if (!empty($error->backtrace[1]['line'])) {
            $message .= ' at line ' . $error->backtrace[1]['line'];
        }
        $message .= ')';
    }

    $logger->log($message, $error->code);
}

PEAR::setErrorHandling(PEAR_ERROR_CALLBACK, 'errorHandler');
PEAR::raiseError('This is an information log message.', PEAR_LOG_INFO);

6   Custom Handlers

There are times when the standard handlers aren't a perfect match for your needs. In those situations, the solution might be to write a custom handler.

6.1   Using a Custom Handler

Using a custom Log handler is very simple. Once written (see Writing New Handlers and Extending Existing Handlers below), you have the choice of placing the file in your PEAR installation's main Log/ directory (usually something like /usr/local/lib/php/Log or C:\php\pear\Log), where it can be found and use by any PHP application on the system, or placing the file somewhere in your application's local hierarchy and including it before the the custom Log object is constructed.

6.1.1   Method 1: Handler in the Standard Location

After copying the handler file to your PEAR installation's Log/ directory, simply treat the handler as if it were part of the standard distributed. If your handler is named custom (and therefore implemented by a class named Log_custom):

require_once 'Log.php';

$logger = Log::factory('custom', '', 'CUSTOM');

6.1.2   Method 2: Handler in a Custom Location

If you prefer storing your handler in your application's local hierarchy, you'll need to include that file before you can create a Log instance based on it.

require_once 'Log.php';
require_once 'LocalHandlers/custom.php';

$logger = Log::factory('custom', '', 'CUSTOM');

6.2   Writing New Handlers

Writing a new Log handler is as simple as authoring a new class that extends the Log class and that implements a relatively small set of standard methods.

Every handler's class name must start with Log_ in order for it to be recognized by the Log package.

class Log_custom extends Log

The handler's constructor will be called with four parameters. These values are discussed in detail in the Configuring a Handler section.

Log_custom($name, $ident = '', $conf = [], $level = PEAR_LOG_DEBUG)

The constructor is responsible for configuring the handler based on these values. Handler-specific parameters are passed as part of the $conf array. At a minimum, the handler's constructor must set the following values defined by the Log base class:

$this->id = md5(microtime().rand());
$this->name = $name;
$this->ident = $ident;
$this->mask = Log::MAX($level);

The Handler Methods section below details the various standard methods that can be implemented by a log handler. The Utility Methods section describes some useful utility methods provided by the Log base class which may be useful when implementing a log handler.

6.3   Extending Existing Handlers

Extending existing handlers is very similar to writing new handlers with the exception that, instead of inheriting from the Log base class directly, the handler extends an existing handler's class. This is a useful way of adding some custom behavior to an existing handler without writing an entirely new class (in the spirit of object-oriented programming).

For example, the mail handler could be extended to support sending messages with MIME-encoded attachments simply by authoring a new Log_mail_mime class with a compliant constructor and a custom log() method. The rest of the standard methods would fall back on the Log_mail base class's implementations.

Obviously, the specific details involved in extending an existing handler require a good working understanding of that handler's implementation.

6.4   Handler Methods

6.4.1   bool open()

The open() method is called to open the log resource for output. Handlers can call open() immediately upon construction or lazily at runtime (perhaps when the first log event is received).

The Log base class provides a protected $_opened member variable which should be set to true when the log handler is opened and false when it is closed. Handler methods can inspect this value to determine whether or not the handler is currently open and ready for output.

If the open() method fails to ready the handler for output, it should return false and set $this-_opened to false.

6.4.2   bool close()

The close() method is called to close the log resource. This method is the analog of the open() method. It should be safe to call close() even when the handler is not open for output.

If the close() method fails to close the handler, it should return false. Otherwise, it should return true. The $this->opened flag should also be updated appropriately.

6.4.3   bool flush()

The flush() method flushes any buffered log events, as described in Flushing Log Events. The implementation of this method will be largely handler-specific. If the handler does not support buffered output, implementing this method is not necessary; the Log class's flush() method will be called instead.

6.4.4   bool log($message, $priority = null)

The log() method is the core of every log handler. It is called whenever the user wishes to log an event. The implementation of this method is very handler-specific. It should return true or false, depending on whether or not the message was successfully logged by the handler.

The log() implementation should be sure to call announce() whenever an event is successfully logged.

6.5   Utility Methods

These utility methods are provided by the Log base class and provide common, useful functionality to handler implementations.

6.5.1   string extractMessage($message)

This method returns the string representation of the provided message data.

If $message is an object, _extractMessage() will attempt to extract the message text using a known method (such as a PEAR_Error object's getMessage() method). If a known method, cannot be found, the serialized representation of the object will be returned.

If the message data is already a string, it will be returned unchanged.

6.5.2   string format($format, $timestamp, $priority, $message)

This method produces a formatted log line based on a format string and a set of tokens representing the current log record and state.

6.5.3   bool isMasked($priority)

This method checks if the given priority is included in the handler's current level mask. This is useful for determining whether or not a log event should be written to the handler's log.

6.5.4   void announce($event)

This method informs any registered log observers that a new event has been logged. $event is an array containing two named elements:

['priority' => $priority, 'message' => $message]

announce() should be called from a handler's log() method whenever an event is successfully logged. Otherwise, registered observers will never become aware of the event.