Undefined variable issue - php

Question

There are 3 compilation errors in the init.php code:
Undefined variable $ind
Undefined variable $popsize
Undefined variable $chrom
How to solve this issue in the proper way?
main.php
include_once 'init.php';
class Individual {
public $genes = array();
//...
}
class Population {
public $ind = array();
public $ind_ptr;
public function setIndPtr(Individual $ind) {
$this->ind_ptr = $ind;
}
}
$popsize = 10;
$chrom = 5;
$pop = new Population();
$pop_ptr = new Population();
$pop = init(pop_ptr);
init.php
function init(Population $pop_ptr) {
$pop_ptr->setIndPtr($ind[0]);
for ($i = 0 ; $i < $popsize ; $i++) {
for ($j = 0; $j < $chrom; $j++) {
$d = rand(0,1);
if($d >= 0.5) {
$pop_ptr->ind_ptr->genes[$j] = 1;
}
else {
$pop_ptr->ind_ptr->genes[$j] = 0;
}
}
$pop_ptr->setIndPtr($ind[$i+1]);
}
$pop_ptr->setIndPtr($ind[0]);
return $pop_ptr;
}

Answer 1

Its a matter of scope: Variables are not shared over files, unless you make them global!
(Badly explained) variables such as
inc.php
$a=1;
main.php
include "inc.php";
print $a
would work
however
inc.php
function func()
{
$a=1;
}
main.php
include "inc.php";
func();
print $a;
a is not available.
Hope that makes it clearer.

Answer 2

Global variables in function scope need to be declared explicitly global before use:
<?php
function foo()
{
global $global_variable_from_outside_function_scope;
$global_variable_from_outside_function_scope += 1;
}
As for $ind, there's no such variable there. You want something more akin to $pop_ptr -> ind. Read the PHP docs again on classes, scope, etc..