Fatal error: Can't use method return value in write context

It turns out that the PHP empty function cannot accept the return value from another function so you have to first define the variable before passing it to the empty() function.

// will generate a fatal error
empty(nl2br($string));
empty($obj->getSomeValue());

// will work
$val = nl2br($string);
$val = $obj->getSomeValue();
empty($val);

Alternatively, you can use the following function instead:

/**
 * Determines whether a variable is considered to be empty,
 * additionally accepts returned values from functions
 *
 * @param mixed	$val	The value to evaluate
 * @return boolean
 */
function empty_return($val) {
	return empty($val);
}

// example
empty_return(nl2br($string));

A more convenient method is to create a wrapper for the console that you can call instead.

This method creates a function called log which can be called from your javascript and takes the first argument as the console command you want to execute and then any number of extra parameters which are passed to the command.

log('log', 'test');  // console.log('test');

log('info', 'something', 'else');  // console.info('something', 'else');

log('group', 'A Group');  // console.group('A Group);

log('groupEnd');  // console.groupEnd();

All commands in the Firebug Console API commands are supported and they way the wrapper is built means that any new ones added in the future will also be supported.

Additional functionality of the wrapper includes being able to turn off console output completely for when you don’t want your debugging to be output and a default command which lets you use the console without specifying a method to execute. For example, most of my logging is done using console.log so instead of having to write log('log', 'something') each time, I can just use log('something') and it will know that the first argument is not a valid console command and use the default option instead.

// log.js

(function(enableLog) {

	/**
	 * The default command, if the first argument is not a valid console command
	 * it will be output as this
	 */
	var defaultCommand = 'log';

	/**
	 * Executes a console command
	 */
	function applyCommand(command, args) {

		/**
		 * if the command is a valid console command
		 */
		if (!!console[command] && typeof console[command] === 'function') {

			// execute the command
			console[command].apply(this, args);

			// return true
			return true;

		}

		// return false because the command did not exist
		return false;

	}

	// define the function in the global scope
	window.log = function() {

		// if logging is enabled and console exists
		if (enableLog && !!window.console) {

			// convert arguments to array
			var args = Array.prototype.slice.call(arguments);

			// remove first item in args - this should be the console command
			var command = args.shift();

			// call the command
			if (!applyCommand(command, args)) {

				// add first item back to args as it wasn't the command
				args.unshift(command);

				// call default command
				applyCommand(defaultCommand, args);

			}

		}

	};

})(true); // true to output to console, false to suppress

Minified version:

(function(d){function c(a,b){if(console[a]&&typeof console[a]==="function"){console[a].apply(this,b);return true}return false}window.log=function(){if(d&&window.console){var a=Array.prototype.slice.call(arguments),b=a.shift();if(!c(b,a)){a.unshift(b);c("log",a)}}}})(true);

Each script that returns a FirePHP log will generate it’s own group in the Firebug console which is expanded by default which means if you are logging a lot of data on the server side (such as database queries) then there will be a lot of data displayed in the console which you may not want to see all the time.

My solution to this was to edit the FirePHP extension so that each script response is collapsed automatically. You can then click a response to expand it if you want to view more details.

In order to do this you will need to edit the RequestProcessor.js file in the FirePHP install directory which should located inside your Firefox profile folder at: extensions\FirePHPExtension-Build@firephp.org\chrome\content\firephp\RequestProcessor.js

You will need to edit line 411 which reads:

    Firebug.Console.openGroup([URL], null, "firephpRequestGroup", null, true);

and change it to:

    var row = Firebug.Console.openGroup([URL], null, "firephpRequestGroup", null, true);
    removeClass(row, "opened");

Once you save these changes you can just restart Firefox and now each FirePHP group will be collapsed by default.

If you would like to be able to toggle on and off automatic collapsing then you can do so by navigating your browser to about:config and adding a boolean preference key with the name extensions.firephp.collapse. Then replace line 411 in RequestProcessor.js with:

	var row = Firebug.Console.openGroup([URL], null, "firephpRequestGroup", null, true);

	if (FirePHP.getPref(FirePHP.prefDomain, 'collapse')) {
		removeClass(row, "opened");
	}

If the extensions.firephp.collapse is true the response will be collapsed, if it is false then it will be expanded.

Finally, a word of warning. If a new version of FirePHP is released and you install it, these changes will be overwritten and will need to be applied again.

SELECT TO_DAYS(date1) - TO_DAYS(date2);

-- example
SELECT TO_DAYS('2010-01-03') - TO_DAYS('2010-01-01'); -- returns '2'

This will give the same effect as DATEDIFF(date1, date2) by converting each date to the number of days since year 0 and subtracting them.

Note: According the MySQL manual, TO_DAYS() is not intended for use with dates that precede the year 1582 because it does not take into account the days that were lost when the Gregorian calendar was introduced so using this method is not advisable for dates earlier than this.