Call to undefined function in Class

Question

<?php

class getCatlist
{
    function catList()
    {
        global $db;

        try {               
            $stmt2 = $db->query("SELECT c.id, c.name, c.slug, c.parent, COUNT(b.catID) AS Total FROM categories c LEFT JOIN blog_post_cats b ON b.catID = c.id GROUP BY c.id HAVING Total > 0");                          
            $row_count = $stmt2->rowCount();
            if ($row_count >= 0) {
                $rows = $stmt2->fetchAll(PDO::FETCH_ASSOC);                   
            }        

        } catch (PDOException $e) {
            echo $e->getMessage();  
        }

        $items = $rows;
        $id = '';
        echo "<ul>";
        foreach ($items as $item) {
            if ($item['parent'] == 0) {            
                echo "<li><a href='category-".$item['slug']."'>".$item['name']." (".$item['Total'].")</a>";
                $id = $item['id'];
                sub($items, $id);
                echo "</li>";            
            }
        }
        echo "</ul>";     
    }

    function sub($items, $id){         
        foreach ($items as $item) {
            if ($item['parent'] == $id) {                 
                echo "<ul>";                                  
                echo "<li><a href='category-".$item['slug']."'>".$item['name']." (".$item['Total'].")</a></li>";           
                sub($items, $item['id']);
                echo "</ul>";
            }
        }        
    } 
}
?>

I call this class with these function catList() and function sub($items, $id)

with that:

<?php
    $cat = new getCatlist();
    $cat->catList();
    $cat->sub();    
?>

But server give me this error: Call to undefined function sub() . So what's wrong with my code? What I miss? And how to I define this: function sub().

I tried and search this calling methods from class things but I didn't solve my problem. So I hope I find in here the solution. Thanks.

Answer 1

The same error can be reproduced with a smaller bit of code like this:

<?php

class Foo{
    public function baz(){
        bar();
    }

    public function bar(){
        echo "boo";
    }
}

$foo  = new Foo();

$foo->baz();

PHP Fatal error: Uncaught Error: Call to undefined function bar() in /home/hpierce/PhpstormProjects/Temp/addNumbers.php:5

That error is talking about the reference to bar() on 5th line, stored within the class, not the method call on the Foo object:

class Foo{
    public function baz(){
        bar();  //<--- This!
    }

//...
}

$foo->baz(); // <-- NOT this.

In PHP, referencing a method of a class from within the class requires the function call to be prefixed with $this->. Without using that PHP is attempting to use a function defined in the global namespace, where there isn't a function named sub().

This is different from languages like Java, where functions can be referenced without an explicit self reference.

The above code can be fixed like this:

<?php

class Foo{
    public function baz(){
        $this->bar();
    }

    public function bar(){
        echo "boo";
    }
}

$foo  = new Foo();

$foo->baz();