Reading and Opening Files¶

So first, how can we load the contents of a file in PHP? The answer is with the file_get_contents function. When we pull up its documentation, we can see how easy it is. Its only required argument is a filename. It opens up that file and returns its contents to us as a string.

Easy! Let’s use it and set the contents to a new variable! To see if it’s working, we’ll use our trusty var_dump:

$petsJson = file_get_contents('pets.json');
var_dump($petsJson);die;

When we refresh, we see the beautiful JSON string!

Warning and Errors in PHP¶

To experiment, let’s change the filename and see what happens if the file doesn’t exist:

$petsJson = file_get_contents('dinosaurs.json');
var_dump($petsJson);die;

this time, we see a warning from PHP:

Warning: file_get_contents(dinosaurs.json): failed to open stream: No such file or directory in /path/to/index.php on line 16

PHP has both errors and warnings when things go wrong. The only difference is that if the code mistake isn’t too bad, PHP just gives us a warning and tries to keep executing our code.

Booleans: True and False¶

Here it continues, and executes our var_dump, which returns false. If we look at the documentation again, we see that file_get_contents returns the contents of the file as a string or it returns false if it couldn’t read the file. false is called a Boolean, which is our fourth PHP data type. To review, we have:

1. Strings, like $var = 'Hello World';
2. Numbers, like $var = 5;. And actually, numbers are sub-divided into integers, like 5, and floats, which have decimals like 5.12. But most of the time in PHP, you don’t care about this.
3. Arrays, like $var = array('puppy1', 'puppy2', 4);
4. And now our 4th type: Booleans. Booleans are simple because there are only two possible values: true and false:

$fileExists = false;
$iLikeKittens = true;

Like with the other 3 data types, we can assign Booleans to variables and functions can return Booleans. file_get_contents returns a string or false, which we now know is a boolean type.

Decoding JSON into an Array¶

Phew! Let’s get back to our furry friends. First, fix the filename. Remember that the JSON contents we’re reading from the file are a string and what we really want is to transform that JSON string into a PHP array. We used json_encode to turn an array into JSON, so it makes sense that we can use json_decode to go the other direction:

$petsJson = file_get_contents('pets.json');
$pets = json_decode($petsJson);
var_dump($pets);die;

When we refresh, it mostly looks right. But instead of an array, it says something about a “stdClass”. This is a PHP object, which you don’t need to worry about now. Instead, if we look at the json_decode docs, we see it has an optional second argument, which is a bool or Boolean that defaults to false. If we change this to true, the function should return an associative array:

$petsJson = file_get_contents('pets.json');
$pets = json_decode($petsJson, true);
var_dump($pets);die;

Perfect! This is the exact array we were building by hand, so remove that along with the var_dump statement:

<?php
    $petsJson = file_get_contents('pets.json');
    $pets = json_decode($petsJson, true);

    // delete all the other $pet1 and $pets variables

    $pets = array_reverse($pets);

    $cleverWelcomeMessage = 'All the love, none of the crap!';
    $pupCount = count($pets);
?>

When we refresh, our page is back! The JSON string is read from the file and then converted into a PHP array. Our code is ready to iterate over each pet in that array and print out its information by using each pet’s keys. This works because the information in the JSON file exactly matches the PHP array we had before.

If we changed the filename key for each pet in our data source pets.json, then we would also need to change it in our application to match:

[
    {
        "image": "pancake.png",
    },
]

<!-- ... index.php -->

<?php foreach ($pets as $cutePet) { ?>
    <div class="col-md-4 pet-list-item">
        <!-- ... -->

        <img src="/images/<?php echo $cutePet['image']; ?>" class="img-rounded">

        <!-- ... -->
    </div>
<?php } ?>

Directory Path to a File¶

Refresh to make sure this still works. Before we finish, let’s play with the PHP file-handling functions a little. First, move pets.json into a new directory called data and refresh. Oh no, things blow up!

Warning: Invalid argument supplied for foreach() in /path/to/index.php on line 87

PHP no longer finds our file, which sets off a chain reaction of terrible things! First, file_get_contents returns false. Of course, false isn’t a valid JSON string, so json_decode chokes as well and doesn’t return an array like it normally would. Finally, we try to loop with foreach, but $pets isn’t even an array. Woh! The moral is that sometimes a mistake in one spot will result in an error afterwards. So don’t just look at the line number of the error: look at the lines above it as well.

To fix this, we can just change our file path to data/pets.json:

$petsJson = file_get_contents('data/pets.json');

When we refresh, everyone is happy again! Notice that file_get_contents looks for files relative to the one being executed. We’ll play with file paths more later, just don’t think it’s magic. PHP is happily stupid: it looks for files right in the directory of this one.

Saving to a File¶

And what if you want to save data to a file? If we go back to the docs for file_get_contents, you’ll see a related function: file_put_contents. It’s also really simple: you give it a filename and a string, and it saves that string to that file. I’ll let you try this on your own in the activities. Don’t worry about its optional arguments.

Other ways to Read and Save Files¶

PHP has a bunch of other file-handling functions beyond file_get_contents and file_put_contents. These include fopen, fread, fwrite and fclose. For now, just forget these exist. Except for when you’re dealing with very large files, these functions accomplish the exact same thing as file_get_contents and file_put_contents, they’re just harder and weirder to use. To make matters worse, most tutorials on the web teach you to use these functions. Madness! You’ll probably use them someday, but forget about them now. Working with files in PHP we need only our 2 handy functions.