Use a class and object-oriented PHP5 code

There's no reason not to write clean, object-oriented PHP5 code. PHP4 support will phase out after the next release (WP 3.1). Of course, you can prefix all your function names to end up with endlessly_long_function_names_with_lots_of_underscores, but it's much easier to just write a simple class and bundle everything in that. Also, put your class in a separate file and name it accordingly so you can easily extend and maintain it:

// in functions.php
require 'inc/class-my-cool-plugin.php';
new MyCoolPlugin();

// in inc/class-my-cool-plugin.php
class MyCoolPlugin {
    function __construct() {
        // add filter hooks, wp_enqueue_script, etc.
        
        // To assign a method from your class to a WP 
        // function do something like this
        add_action('admin_menu', array($this, "admin"));
    }
    
    public function admin() {
        // public methods, for use outside of the class
        // Note that methods used in other WP functions 
        // (such as add_action) should be public
    }
    
    private function somethingelse() {
        // methods you only use inside this class
    }
}

Use a class and object-oriented PHP code

There's no reason not to write clean, object-oriented PHP code. PHP4 is not supported since 2008. Of course, you can prefix all your function names to end up with endlessly_long_function_names_with_lots_of_underscores, but it's much easier to just write a simple class and bundle everything in that. Also, put your class in a separate file and name it accordingly so you can easily extend and maintain it:

// in functions.php
require 'inc/class-my-cool-plugin.php';
new MyCoolPlugin();

// in inc/class-my-cool-plugin.php
class MyCoolPlugin {
    function __construct() {
        // add filter hooks, wp_enqueue_script, etc.
        
        // To assign a method from your class to a WP 
        // function do something like this
        add_action('admin_menu', [$this, "admin"]);
    }
    
    public function admin() {
        // public methods, for use outside of the class
        // Note that methods used in other WP functions 
        // (such as add_action) should be public
    }
    
    private function somethingelse() {
        // methods you only use inside this class
    }
}

Use a class and object orientated PHP5 code

There's no reason not to write clean, object-orientated PHP5 code. PHP4 support will phase out after the next release (WP 3.1). Of course, you can prefix all your function names to end up with endlessly_long_function_names_with_lots_of_underscores, but it's much easier to just write a simple class and bundle everything in that. Also, put your class in a seperate file and name it accordingly so you can easily extend and maintain it:

// in functions.php
require 'inc/class-my-cool-plugin.php';
new MyCoolPlugin();

// in inc/class-my-cool-plugin.php
class MyCoolPlugin {
    function __construct() {
        // add filter hooks, wp_enqueue_script, etc.
        
        // To assign a method from your class to a WP 
        // function do something like this
        add_action('admin_menu', array($this, "admin"));
    }
    
    public function admin() {
        // public methods, for use outside of the class
        // Note that methods used in other WP functions 
        // (such as add_action) should be public
    }
    
    private function somethingelse() {
        // methods you only use inside this class
    }
}
    

Use a class and object-oriented PHP5 code

There's no reason not to write clean, object-oriented PHP5 code. PHP4 support will phase out after the next release (WP 3.1). Of course, you can prefix all your function names to end up with endlessly_long_function_names_with_lots_of_underscores, but it's much easier to just write a simple class and bundle everything in that. Also, put your class in a separate file and name it accordingly so you can easily extend and maintain it:

// in functions.php
require 'inc/class-my-cool-plugin.php';
new MyCoolPlugin();

// in inc/class-my-cool-plugin.php
class MyCoolPlugin {
    function __construct() {
        // add filter hooks, wp_enqueue_script, etc.
        
        // To assign a method from your class to a WP 
        // function do something like this
        add_action('admin_menu', array($this, "admin"));
    }
    
    public function admin() {
        // public methods, for use outside of the class
        // Note that methods used in other WP functions 
        // (such as add_action) should be public
    }
    
    private function somethingelse() {
        // methods you only use inside this class
    }
}