How do you debug PHP scripts? [closed]

Answer 1

This is my little debug environment:

error_reporting(-1);
assert_options(ASSERT_ACTIVE, 1);
assert_options(ASSERT_WARNING, 0);
assert_options(ASSERT_BAIL, 0);
assert_options(ASSERT_QUIET_EVAL, 0);
assert_options(ASSERT_CALLBACK, 'assert_callcack');
set_error_handler('error_handler');
set_exception_handler('exception_handler');
register_shutdown_function('shutdown_handler');

function assert_callcack($file, $line, $message) {
    throw new Customizable_Exception($message, null, $file, $line);
}

function error_handler($errno, $error, $file, $line, $vars) {
    if ($errno === 0 || ($errno & error_reporting()) === 0) {
        return;
    }

    throw new Customizable_Exception($error, $errno, $file, $line);
}

function exception_handler(Exception $e) {
    // Do what ever!
    echo '<pre>', print_r($e, true), '</pre>';
    exit;
}

function shutdown_handler() {
    try {
        if (null !== $error = error_get_last()) {
            throw new Customizable_Exception($error['message'], $error['type'], $error['file'], $error['line']);
        }
    } catch (Exception $e) {
        exception_handler($e);
    }
}

class Customizable_Exception extends Exception {
    public function __construct($message = null, $code = null, $file = null, $line = null) {
        if ($code === null) {
            parent::__construct($message);
        } else {
            parent::__construct($message, $code);
        }
        if ($file !== null) {
            $this->file = $file;
        }
        if ($line !== null) {
            $this->line = $line;
        }
    }
}

Answer 2

In all honesty, a combination of print and print_r() to print out the variables. I know that many prefer to use other more advanced methods but I find this the easiest to use.

I will say that I didn't fully appreciate this until I did some Microprocessor programming at Uni and was not able to use even this.

Answer 3

There are many PHP debugging techniques that can save you countless hours when coding. An effective but basic debugging technique is to simply turn on error reporting. Another slightly more advanced technique involves using print statements, which can help pinpoint more elusive bugs by displaying what is actually going onto the screen. PHPeclipse is an Eclipse plug-in that can highlight common syntax errors and can be used in conjunction with a debugger to set breakpoints.

display_errors = Off
error_reporting = E_ALL 
display_errors = On

and also used

error_log();
console_log();

Answer 4

The most of bugs can be found easily by simply var_dumping some of key variables, but it obviously depends on what kind of application you develop.

For a more complex algorithms the step/breakpoint/watch functions are very helpful (if not necessary)

Answer 5

In a production environment, I log relevant data to the server's error log with error_log().

Answer 6

Xdebug, by Derick Rethans, is very good. I used it some time ago and found it was not so easy to install. Once you're done, you won't understand how you managed without it :-)

There is a good article on Zend Developer Zone (installing on Linux doesn't seem any easier) and even a Firefox plugin, which I never used.