At some point in your PHP development you are likely to want to break repeated functionality out into a separate, well, function. Something that you’ll no doubt also want to do is pass information back and forward from these functions.
If you are familiar with scope in programming you will be aware that variables are typically only available where they are created. This means if you create a variable called $name in the main part of your code you would not be able to “see” this variable in a function unless you passed it across. The scope of the variable is limited.
In many languages there is the concept of a global scope that allows you to make a variable available globally so you would be able to access it anywhere. This is frowned upon in PHP so how do you get variables in and out of functions? In the rest of this article I show you through a number of different examples.
Passing No Parameters
In this simple example we have a function called get_user that will eventually return user information. Here we are passing no parameters and all the function does is print out the words ‘hello world!’.
This is not particularly useful but does illustrate the concept.
function get_user(){
echo 'hello world!';
}
get_user();
This would output:
hello world!
Passing One or More Parameter
Next we want to pass in one or more parameter which we do by including the name in the brackets after the function name. It is important to note that these names are what they are referred to in the function and not in the calling code.
function get_user($firstname, $lastname){
echo 'hello ;.$firstname.' '.$lastname;
}
get_user('Neil', 'Thompson');
Running this would output:
hello Neil Thompson
Setting Defaults for Passed Parameters
It is also possible to set default parameters for variables that you are passing into a function. These can also be null if you wanted.
function get_user($firstname='Fred', $lastname='Bloggs'){
echo 'hello ;.$firstname.' '.$lastname;
}
get_user('Neil', 'Thompson');
get_user();
Running this would output:
hello Neil Thompson hello Fred Bloggs
Returning a Single Response
So you have passed in some parameters but how do you get something out? For that you need to use the return statement which returns control to whatever called the function.
You don’t need to return anything but if you need to then you do so immediately after the return statement as shown below. Important note you can return one and only one item which seems a bit restrictive but we’ll get to that below.
function get_user($firstname='Fred', $lastname='Bloggs'){
return ucwords($firstname.' '.$lastname);
}
$response = get_user('neil', 'thompson');
echo $response;
Running this would output:
Neil Thompson
Returning Multiple Responses #1
One of the restrictions of the return statement is that you can return one and only one variable. On the face of it this seems pretty limiting but there are ways around this. The first is to return an array or even an array of arrays and unpack that. For example:
function get_user($firstname='Fred', $lastname='Bloggs'){
$response = array('first'=> ucwords($firstname), 'last'=>ucwords($lastname));
return $response;
}
$response = get_user('neil', 'thompson');
print_r($response);
Running this would output:
Array ( [first] => Neil [last] => Thompson )
A slightly more complicated example with nested arrays:
function get_user($firstname='Fred', $lastname='Bloggs'){
$response = array('proper' => array('first'=> ucwords($firstname), 'last'=> ucwords($lastname)),
'upper' => array('first'=> strtoupper($firstname), 'last'=> strtoupper($lastname)));
return $response;
}
$response = get_user('neil', 'thompson');
print_r($response['upper']);
$proper = $response['proper'];
Running this would output:
Array (
[upper] => Array (
[first] => NEIL
[last] => THOMPSON
)
)
Returning Multiple Responses #2
The above example is a bit contrived and there is a better way to deal with these sorts of multiple returns using the not very helpfully named list function. What this effectively does it split out the arrays as shown above into separate variables. Let’s take a look.
function get_user($firstname='Fred', $lastname='Bloggs'){
$response = array('proper' => array('first'=> ucwords($firstname), 'last'=> ucwords($lastname)),
'upper' => array('first'=> strtoupper($firstname), 'last'=> strtoupper($lastname)));
return $response;
}
list($proper, $upper) = get_user('neil', 'thompson');
print_r($upper);
Running this would output:
Array (
[upper] => Array (
[first] => NEIL
[last] => THOMPSON
)
)
So in the above snippet the function is returning two arrays which are then separated out by the list command and placed in the two new variables shown.
By combining all the features shown here you should be able to easily pass in and out as many variables to a function as you need. Happy coding!