<?php
$global_array = array();
$productsPerCategory = array(
    "fruits"     => array("banana", "mango", "orange"),
    "vegatables" => array("carrot", "potato", "lettuce"),
    "meat"       => array("pork", "beef")
);
 
function data($products){
    global $global_array;   // <-- reference the global variable '$global_array'
                            // (omitting this will create a new, empty, local variable)
    forEach ($products as $key => $value) {
        $global_array[] = $value;
    }
}
 
forEach ($productsPerCategory as $category => $products) {
    data($products);
}
 
var_dump($global_array);
?>
 

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