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63 lines
1.4 KiB
Markdown
63 lines
1.4 KiB
Markdown
A function allows you to store code under a name and then execute
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that code later.
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A function always starts with the
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function keyword followed by the name with parentheses and then
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opening and closing curly braces around the code.
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```php
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<?php
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function hello_world() {
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echo "hello world\n";
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}
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```
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To call the function, use the function name with parentheses.
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```php
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hello_world();
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```
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You can set up values to be passed into a function.
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To do so, write variables in between the function parentheses.
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Each one should be separated by a comma.
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```php
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function greet($firstname, $lastname) {
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echo "hello $firstname $lastname\n";
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}
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```
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Then, you can pass in values when calling a function. In the greet function,
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'John' is assigned to `$firstname` and 'Smith' is assigned to
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`$lastname`.
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```php
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greet('John', 'Smith');
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```
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You can also return a value from a function. You can only
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return a single value from a function.
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```php
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function capitalize($value) {
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return strtoupper($value);
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}
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```
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When calling a function, it will output the return value which
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you can load into a variable.
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```php
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$animal = capitalize('dog');
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echo "$animal\n";
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```
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You can also create nameless functions called closures. Closures can be
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stored in variables or passed into other functions.
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```php
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$sum = function ($a, $b) {
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return $a + $b;
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};
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```
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You can execute a closure by putting parentheses after the variable.
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```php
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echo $sum(1, 2) . "\n";
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```
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