Variable Variables

Suppose you need to output a variable but you don’t know in advance which variable it. Take a look at this code:
<br /> $hello = “Hello there!”;<br /> $hey = “Hey you!”;<br /> $greet = “hello”;</p> <p>if ($greet == “hello”)<br /> echo $hello;<br /> else if ($greet == “hey”)<br /> echo $hey;<br />
Using variable variables, you can rewrite the above as follows:
<br /> $hello = “Hello there!”;<br /> $hey = “Hey you!”;<br /> $greet = “hello”;</p> <p>echo $$greet;
Because $greet == “hello”, the end of the script runs as if it were echo $hello. More details on variable variables here.

Dynamic Functions/Objects

The same principle described above can also be applied to functions, member variables, and functions, and object instantiation. Check this out:
<br /> // Dynamic functions<br /> function test() {<br /> echo “This function can be called dynamically!”;<br /> }<br /> $function_name = “test”;<br /> $function_name();</p> <p>// Dynamic member variables, functions, and objects<br /> class TestClass<br /> {<br /> public $testvar = “Property of an object.”;</p> <p> public function testfunc($text) {<br /> echo $text;<br /> }<br /> }</p> <p>$dynobj = “TestClass”;<br /> $dynvar = “testvar”;<br /> $dynfunc = “testfunc”;</p> <p>// Dynamic object instantiation<br /> $obj = new $dynobj();</p> <p>// Dynamic member variable access<br /> echo $obj->$dynvar;</p> <p>// Dynamic member function access<br /> $obj->$dynfunc(“Wow, this works!”);
Isn’t that exciting? Gotta love PHP for making it so easy!