Basic logging for PHP in JSON to stdout with Loglevel configurable from environment variables.

Log.php

<?php

$LOGLEVEL = 5;

if( isset($_SERVER['LOGLEVEL']) && is_numeric(Log::LEVELS[$_SERVER['LOGLEVEL']])){
    $LOGLEVEL = Log::LEVELS[$_SERVER['LOGLEVEL']];
}

abstract class Log
{
    const LEVELS = array(
        "ALL" => 0,
        "TRACE" => 1,
        "DEBUG" => 2,
        "INFO" => 3,
        "WARN" => 4,
        "ERROR" => 5
    );
}

function trace($msg){
    if($GLOBALS['LOGLEVEL'] > Log::LEVELS['TRACE']) return;
    formatAndPrint("TRACE", $msg);
}

function debug($msg){
    if($GLOBALS['LOGLEVEL'] > Log::LEVELS['DEBUG']) return;
    formatAndPrint("DEBUG", $msg);
}

function info($msg){
    if($GLOBALS['LOGLEVEL'] > Log::LEVELS['INFO']) return;
    formatAndPrint("INFO", $msg);
}

function warn($msg){
    if($GLOBALS['LOGLEVEL'] > Log::LEVELS['WARN']) return;
    formatAndPrint("WARN", $msg);
}

function error($msg, $exception = null){
    if($GLOBALS['LOGLEVEL'] > Log::LEVELS['ERROR']) return;

    formatAndPrint("ERROR", $msg, $exception);
}

function formatAndPrint( $level, $msg, $exception = null)
{
    $obj = array(
        "timestamp" => date(DateTime::ISO8601),
        "level" => $level,
        "msg" => $msg,
    );

    if(isset($exception))
        $obj['exception'] = $exception->getMessage();

    $flags = JSON_UNESCAPED_SLASHES;
    if($GLOBALS['DEVELOPMENT'])
        $flags = $flags | JSON_PRETTY_PRINT;

    $message = json_encode($obj, $flags);
    file_put_contents("php://stdout" , $message.PHP_EOL);
}

/*
## Usage

### somewhere you load libraries..

`require('./Log.php');`

### in the environment

LOGLEVEL in ("ALL", "TRACE", "DEBUG", "INFO", "WARN", "ERROR") # default is ERROR
DEVELOPMENT in (true, false) # pretty-print json in logs, default is false

### put this wherever

trace("THIS IS A trace message");
debug("THIS IS A debug message");
info("THIS IS A info message");
warn("THIS IS A warn message");
error("THIS IS A error message");
error("THIS IS A error message", new Exception("With Exception"));

## Example output
{
    "timestamp": "2021-01-07T21:13:21+0000",
    "level": "WARN",
    "msg": "THIS IS A warn message"
}
{
    "timestamp": "2021-01-07T21:13:21+0000",
    "level": "ERROR",
    "msg": "THIS IS A error message"
}
{
    "timestamp": "2021-01-07T21:13:21+0000",
    "level": "ERROR",
    "msg": "THIS IS A error message",
    "exception": "With Exception"
}

*/

I wanted basic logging in PHP in JSON format, without installing modules. Loglevel is configurable from the environment.

Use this e.g. if you want to run PHP in a Docker container, and pick up the logs with DataDog or similar.

I'm sharing this because from what I could Google it looks like I'm not the only one that could use something like this.

Rules for usage

• This is provided "as is," I have no intention of maintaining it, use with caution.
• If you have cool suggestions, please post them in a comment and I will consider them if I notice it in my sea of notifications.

---

"Look, Mom, I made a framework!..."

---

Heavily inspired by a tiny logger I wrote for Java https://gitlab.com/com.figaw.util/loglite

and augmented error_logger,

function myErrorHandler( $errType, $errStr, $errFile, $errLine )
{
    $displayErrors = ini_get( 'display_errors' );
    $logErrors     = ini_get( 'log_errors' );

    if( $displayErrors ) echo $errStr.PHP_EOL;

    if( $logErrors )
    {
        $err = array(
            "timestamp" => date(DateTime::ISO8601),
            "error" => $errStr,
            "file" => $errFile,
            "line" => $errLine
        );

        $flags = JSON_UNESCAPED_SLASHES;
        if($GLOBALS['DEVELOPMENT'])
            $flags = $flags | JSON_PRETTY_PRINT;

        $message = json_encode($err, $flags);
        file_put_contents("php://stderr" , $message.PHP_EOL);
    }
}

ini_set( 'log_errors', 1 );
set_error_handler( 'myErrorHandler' );

From: https://stackoverflow.com/a/35400363/1104755