Condition based function declarations

Question

I recently came across a weird piece of code

if(foo == bar){
 function foo_bar(){
   // Function definition
 }
}

Is this a good practice of coding ?

Answer 1

There is one valid use case:

if( !function_exists("helloWorld") ) {
    function helloWorld() {
        ...
    }
}

Other than that, it would be preferable to avoid defining your functions inside if blocks.