PHP var_dump
Summary: in this tutorial, you will learn how to use the PHP var_dump() function to dump the information about a variable.
Introduction to the PHP var_dump function
The var_dump() is a built-in function that allows you to dump the information about a variable. The var_dump() function accepts a variable and displays its type and value.
If you open the page on the web brower, you’ll see the following output:
The output shows the value of the variable (100) and its type (int) which stands for integer.
To make the output more intuitive, you can wrap the output of the var_dump() function in a pre tag like this:
The output now is much more readable.
The dump helper function
It’s kind of tedious to always echo the opening tags when you dump the information about the variable.
To make it easier, you can define a function and reuse it. For now, you can think that a function is a reusable piece of code that can be referenced by a name. A function may have input and also output.
The following defines a function called d() that accepts a variable. It shows the information about the variable and wraps the output in the ‘ ; >
To use the d() function, you can pass a variable to it as follows:
The output is much clean now.
Dump and die using the var_dump() and die() functions
The die() function displays a message and terminates the execution of the script:
Sometimes, you want to dump the information of a variable and terminate the script immediately. In this case, you can combine the var_dump() function with the die() function as follows:
‘ ; die (); echo ‘After calling the die function’ ;
Since the die() function terminates the script immediately, the following statement did not execute:
Therefore, you didn’t see the message in the output.
Now, you can use the dd() function as follows:
In the later tutorial, you will learn how to place the functions in a file and reuse them in any script.
Using Laravel’s dd (dump and die) function in PHP
One of the most common ways to debug an error in PHP ecosystem is to dump the variable on the screen, and figure out what is going wrong with it.
The most common way we do it in PHP is via using var_dump function.
var_dump function dumps all the information about the variable or object on your page, but it does not stop the execution of the program further.
Let’s consider an example where if you have an associate array and you want to dump it on the screen.
This is what you get on the screen.
As you can see our code did not die and also the formatting isn;t very nice.
Using dd in PHP
If you are a laravel developer you must be aware of dd() function, dd dumps and die. There is no dd function in php if you try to do dd($prices) in the above example it will throw an error. Call to undefined function dd()
We can however create our own dd function, that will dump the variable/object and then die the script execution.
We have created a new dd function, and wrapped the var_dump around pre tags so that it gives out a nice formatting in the browser and a more readable dump.
This is how you see the output, and the php scripts die after dumping. It does not execute the further code.
You can isolate this function in a reusable functions file or a Class.
Echoing: dd() vs var_dump() vs print_r()
One of the most popular way of debugging in PHP still remains the same – showing variables in the browser, with hope to find what the error is. Laravel has a specific short helper function for showing variables – dd() – stands for “Dump and Die”, but it’s not always convenient. What are other options?
First, what is the problem with dd()? Well, let’s say we want to get all rows from DB table and dump them:
We would see something like this:
Oh, ok, three rows. Now what are the values? We have to click to expand it – ok, let’s do that:
Mmm, now we know which type we are dealing with – “PaymentMethod”. [sarcasm]really helpful…[/sarcasm]
Let’s expand one of the rows now – maybe we will finally see the values?
Nope. The final step is to expand attributes or original sections.
But you get the point – to see the actual values, we need to click three additional times, and we don’t see the full result without those actions. At first I thought – maybe dd() function has some parameters for it? Unfortunately not. So let’s look at other options:
var_dump() and die()
Good old PHP way of showing the data of any type:
Not easily readable, is it? The trick here is to View Source in browser, in case of Chrome/Windows it’s CTRL+U:
Better, huh? But there’s even more readable way.
print_r()
Another PHP built-in function print_r() has a perfect description for us: “Prints human-readable information about a variable”
And then go to View Source of the browser… We get this:
Now we can read the contents easily and try to investigate the error.
Moreover, print_r() function has another optional parameter with true/false values – you can not only echo the variable, but return it as string into another variable. Then you can combine several variables into one and maybe log it somewhere, for example.
So, in cases like this, dd() is not that convenient – PHP native functions to the rescue. But if you want the script to literally “dump one simple variable and die” – then dd($var) is probably the fastest to type.
Using dd (dump and die) function in PHP
One of the most common ways to debug an error in PHP ecosystem is to dump the variable on the screen, and figure out what is going wrong with it.
The most common way we do it in PHP is via using var_dump function.
var_dump function dumps all the information about the variable or object on your page, but it does not stop the execution of the program further.
Let’s consider an example where if you have an associate array and you want to dump it on the screen.
Exit fullscreen mode
This is what you get on the screen. 
As you can see our code did not die and also the formatting very nice 🤔
Using dd in PHP
Exit fullscreen mode
This is how you see the output, and the php scripts die after dumping. It does not execute the further code. 
You can isolate this function in a reusable functions file or a Class.
I hope you enjoyed the read!
Feel free to follow me on GitHub, LinkedIn and DEV for more!
Компонент VarDumper (сброс переменной)¶
Установка¶
Alternatively, you can clone the https://github.com/symfony/var-dumper repository.
If you install this component outside of a Symfony application, you must require the vendor/autoload.php file in your code to enable the class autoloading mechanism provided by Composer. Read this article for more details.
Функция dump()¶
По умолчанию, формат вывода и направление выбираются исходя из вашего текущего PHP SAPI:
Для того, чтобы функция dump() всегда была доступна при выполнении любого PHP кода, вы можете установить её на вашем компьютере глобально:
New in version 4.1: Метод dd() появился в Symfony 4.1.
Сервер дампов¶
New in version 4.1: Сервер дампов появился в Symfony 4.1.
Функция dump() выводит своё содержимое в то же окно браузера или консольный терминал, что и ваше приложение. Иногда смешение настоящего вывода с выводом отладочной информации может запутывать. Поэтому этот компонент предоставляет сервер для сбора всей отладочной информации.
Интеграция DebugBundle и Twig¶
DebugBundle позволяет большую интеграцию компонента в приложения Symfony.
Но если панель инструментов нельзя отобразить так как вы, к примеру, вызвали die() / exit() / dd() или возникла фатальная ошибка, тогда дампы пишутся в обычном потоке вывода.
В шаблоне Twig доступны две конструкции для сброса переменной. Выбор между двумя в основном зависит от ваших личных предпочтейни, и всё же:
Использование компонента VarDumper в вашем наборе тестов PHPUnit¶
Это предоставит вам два новых утверждения:
New in version 4.1: Возможность передачи нестроковых переменных в качестве первого аргумента assertDumpEquals() была представлена в Symfony 4.1.
Примеры сброса и вывод¶
Для простых переменных, чтение вывода должно быть прямолинейным. Вот некоторые примеры, отображающие первую переменную, определённую в PHP, а потом его представление сброса:
#14 это внутренний объект для обработки. Он позволяет сранвивать два последовательных сброса одного и того же объекта.