PHP全局变量范围使用最佳实践

Question

I am new to programming and have some suspicions regarding the usage of global variables inside functions.

I am trying to separate the logic from the structure of my html form and here is where my question stems from.

The variable I have declared as global will only be used in one specific place from outside of the function, ie the html form.

function updatePosts(){
     $query= "...";
     $result= "...";
     $rows= mysqli_fetch_assoc($result);
     global $post_title;
     $post_title = $rows['post_title'] ;
}

updatePosts();

<form action="">
//use of global variable outside function
    <input type="text" name="" value="{$post_title}" class="form-control">
</form>

When i declared multiple global variables it raised some questions regarding what the impact of so many global variables might be. eg.

function updatePosts(){
     $query= "...";
     $result= "...";
     $rows= mysqli_fetch_assoc($result);
     global $post_title;
     global $post_author;
     global $post_content;
     global $post_tags;
     global $post_image;
     global $post_status;
     global $post_date;
     $post_title = $rows['post_title'] ;
     $post_author = $rows['post_author'] ;
     $post_content = $rows['post_content'] ;
     $post_tags = $rows['post_tags'] ;
     $post_image = $rows['post_image'] ;
     $post_status = $rows['status'] ;
     //and so on..
}

updatePosts();

<form action="">
<input type="text" name="" value="<?php echo $post_title ?>" class="form-control">
<input type="text" name="" value="<?php echo $post_author ?>" class="form-control">
<input type="text" name="" value="<?php echo $post_tags ?>" class="form-control">
<input type="text" name="" value="<?php echo $post_content ?>" class="form-control">
<input type="text" name="" value="<?php echo $post_status ?>" class="form-control">
//and so on...
</form>

Is this considered to be an acceptable usage of functions and global variables?

If not, what might be a more efficient way to separate the logic from the structure. Rather than encapsulating in a function would includes would be better suited for this task?

Any advice would be very much appreciated and would go a long way in helping a beginner on his journey in programming / php.

Answer 1

I personally would use Closures to grab variables in your scope for further use and yes the keyword global is bad practice and in the older version it was more useful in procedual coding but today you just build tiny Closures for quick use.

Just to give you a general idea.

$variable_from_outside = "hi!";
$closure = function() use ($variable_from_outside) {
    // do stuff with that variable inside this scope..
};

Closure Documentation

However, you may also just grab your variables inside your function as parameter

$variable = 'something';
function func($variable) {
    // do stuff with $variable
}

And in OOP, best way are Traits. Declare universal properties or methods and use them in classes whatever your wish is. Also it reduces performance when you take traits in a later derived class for example that way they don't have to be carried in your entire API all the way.

trait Example {
    public $stuff = 'Yey!';
    // or methods...
}

class someClass {
    use Example;
    function __construct() {
        echo $this->stuff; // Yey!
        // etc...
    }
}

Trait Documentation