如何通过变量调用函数

Question

I hope this question is not too simple, but I have no idea how to do this

$book = 'book';
$car = 'car';

function $book()
{ 
 return "Hello, world!";
}
function $car()
{
 return "WoW , The red car";
}

Answer 1

You can call a function with variable name like this:

Variable functions

<?php
    $a = 'book';

    function book() {
        echo 'book function';
    }

    // this is equivalent to book()
    $a();

So to expand a little bit:

<?php
$functions = ['book', 'car'];

function book() {
    return "Hello, world!";
}

function car() {
    return "WoW , The red car";
}

foreach ($functions as $function) {
    echo $function() .'<br>';
}

The OUTPUT would be:

Hello, world!
WoW , The red car

Another way of doing it to get same output:

Anonymous functions

$book = function() {
    echo 'book function';
};

$book();

In this case, the above function doesn't have an actual name and is represented by a variable.

And let me give you an example:

<?php
    $book = function() {
        echo 'book function';
    };

    $a = $book;

    echo $a();

So, to expand in the same manner:

<?php
$functions = ['book', 'car'];

$book = function () {
    return "Hello, world!";
};

$car = function() {
    return "WoW , The red car";
};

foreach ($functions as $function) {
    echo ${$function}(). '<br>';
}

DEMO:

http://sandbox.onlinephpfunctions.com/code/1972f1acd72984d459efbfb308680aaa9d7a1fad