PHP custom function scope / good practice

I have script which has the following structure:

<?php
    if( a == b ){

        function some_function_name(){
            // do something here
        }

        if( c 开发者_Go百科== d ){
            some_function_name();
        }
    }
?>

I get an error message saying that some_function_name(); does not exist.

What am I doing wrong and is this good practice?

I want to create a function, because I have a bunch of steps which I need to use many times, and I would prefer not to have to copy/paste the same code over and over again.

You can not declare function in if-statements.

you could do this:

<?php   
    function some_function_name() {
       // do something here
    }

    if( a == b  && c == d ) {
        some_function_name();
    }
?>

I would avoid defining the function inside a conditional if() statement. Define the function first, at the top of the file and call it when necessary.

If you have a bunch of steps you want to put into function, you have to define function outside the if statements, preferably at the beginning or end of file, or maybe in a seperate file

If this function is a legitimate part of your workflow that will be used from multiple places, make it a top-level function (or a class method if applicable).

In the (relatively infrequent) case that you want to create a function to be passed as a callback, and this function's behavior is mostly to be determined by the values of variables, you can define an anonymous function:

$func = function() {
    // do something here
}

if(c == d){
    // you can call it like this, but read the above paragraph
    $func();
}

Anonymous functions require PHP >= 5.3; if you are using an earlier version you can achieve the same result with create_function, but it's such a hassle that it rarely is worth the trouble.

It's not a good practice, in fact, there is no reason for not defining the function outside the if block. The approach is very error prone.

You are getting the error because some_function_name() bound to the scope of the first if block.

I want to create a function, because I have a bunch of steps which I need to use many times, and I would prefer not to have to copy/paste the same code over and over again.

You shouldn't copy/paste! That's what functions are for. Create your functions and reuse them as much as you want.