How do I log errors and warnings into a file?

Question

Use the following code:

ini_set("log_errors", 1);
ini_set("error_log", "/tmp/php-error.log");
error_log( "Hello, errors!" );

Then watch the file:

tail -f /tmp/php-error.log

Or update php.ini as described in this blog entry from 2008.

See

• error_log — Send an error message somewhere

Example

error_log("You messed up!", 3, "/var/tmp/my-errors.log");

You can customize error handling with your own error handlers to call this function for you whenever an error or warning or whatever you need to log occurs. For additional information, please refer to the Chapter Error Handling in the PHP Manual

Simply put these codes at top of your PHP/index file:

error_reporting(E_ALL); // Error/Exception engine, always use E_ALL

ini_set('ignore_repeated_errors', TRUE); // always use TRUE

ini_set('display_errors', FALSE); // Error/Exception display, use FALSE only in production environment or real server. Use TRUE in development environment

ini_set('log_errors', TRUE); // Error/Exception file logging engine.
ini_set('error_log', 'your/path/to/errors.log'); // Logging file path

Add this code in file .htaccess (as an alternative to file php.ini or the ini_set function):

<IfModule mod_php5.c>
php_flag log_errors on 
php_value error_log ./path_to_MY_PHP_ERRORS.log
# php_flag display_errors on 
</IfModule>

• as commented: this is for Apache-type servers, and not for Nginx or others.

That's my personal short function

# logging
/*
[2017-03-20 3:35:43] [INFO] [file.php] Here we are
[2017-03-20 3:35:43] [ERROR] [file.php] Not good
[2017-03-20 3:35:43] [DEBUG] [file.php] Regex empty

mylog ('hallo') -> INFO
mylog ('fail', 'e') -> ERROR
mylog ('next', 'd') -> DEBUG
mylog ('next', 'd', 'debug.log') -> DEBUG file debug.log
*/
function mylog($text, $level='i', $file='logs') {
    switch (strtolower($level)) {
        case 'e':
        case 'error':
            $level='ERROR';
            break;
        case 'i':
        case 'info':
            $level='INFO';
            break;
        case 'd':
        case 'debug':
            $level='DEBUG';
            break;
        default:
            $level='INFO';
    }
    error_log(date("[Y-m-d H:i:s]")."\t[".$level."]\t[".basename(__FILE__)."]\t".$text."\n", 3, $file);
}

Take a look at the log_errors configuration option in php.ini. It seems to do just what you want to. I think you can use the error_log option to set your own logging file too.

When the log_errors directive is set to On, any errors reported by PHP would be logged to the server log or the file specified with error_log. You can set these options with ini_set too, if you need to.

(Please note that display_errors should be disabled in php.ini if this option is enabled)