Filtering log messages

The following conforms to the PSR-3: Logger Interface document.

The log levels are in order of priority/importance:

• emergency (0)
• alert (1)
• critical (2)
• error (3)
• warning (4)
• notice (5)
• info (6)
• debug (7)

Although the plain Logger in laminas-log is not fully compatible with PSR-3, it provides a way to log all of these message types.

The following example has three file writers using filters:

• First Example: FileWriter - All messages are logged in /log/dk.log
• Second Example: OnlyWarningsWriter - Only warnings are logged in /log/warnings.log
• Third Example: WarningOrHigherWriter - All important messages (warnings or critical) are logged in /log/important_messages.log

<?php

return [
    'dot_log' => [
        'loggers' => [
            'my_logger' => [
                'writers' => [
                    'FileWriter' => [
                        'name' => 'FileWriter',
                        'priority' => \Laminas\Log\Logger::ALERT,
                        'options' => [
                            'stream' => __DIR__ . '/../../log/dk.log',
                            'filters' => [
                                'allMessages' => [
                                    'name' => 'priority',
                                    'options' => [
                                        'operator' => '>=', 
                                        'priority' => \Laminas\Log\Logger::EMERG,
                                    ]
                                ],
                            ],
                        ],
                    ],
                    // Only warnings
                    'OnlyWarningsWriter' => [
                        'name' => 'stream',
                        'priority' => \Laminas\Log\Logger::ALERT,
                        'options' => [
                            'stream' => __DIR__ . '/../../log/warnings_only.log',
                            'filters' => [
                                'warningOnly' => [
                                    'name' => 'priority',
                                    'options' => [
                                        'operator' => '==',
                                        'priority' => \Laminas\Log\Logger::WARN,
                                    ],
                                ],
                            ],
                        ],
                    ],
                    // Warnings and more important messages
                    'WarningOrHigherWriter' => [
                        'name' => 'stream',
                        'priority' => \Laminas\Log\Logger::ALERT,
                        'options' => [
                            'stream' => __DIR__ . '/../../log/important_messages.log',
                            'filters' => [
                                'importantMessages' => [
                                    'name' => 'priority',
                                    'options' => [
                                        // note, the smaller the priority, the more important is the message
                                        // 0 - emergency, 1 - alert, 2- error, 3 - warn etc.
                                        'operator' => '<=',
                                        'priority' => \Laminas\Log\Logger::WARN,
                                    ],
                                ],
                            ],
                        ],
                    ],
                ],
            ],
        ],
    ],
];

As in the writer configuration, the developer can optionally use keys for associating the filters with a name.

IMPORTANT NOTE: the operator for more important messages is <=, this is because the number representation is smaller for a more important message type.

The filter added on the first writer is equivalent to not setting a filter, but it was added to illustrate the usage of the operator to explicitly allow all messages.

More examples on filters: https://docs.laminas.dev/laminas-log/filters/