Php: what's the difference between $var and &$var?

Question

What is the difference between

foreach ($my_array as $my_value) {
}

And:

foreach ($my_array as &$my_value) {
}

Answer 1

Jonathan's answers describes it very well. Just for completeness, here are your two examples:

1. Just reading values:

   $my_array = range(0,3);
   foreach ($my_array as $my_value) {
       echo $my_value . PHP_EOL;
   }
   

2. Adding some number to each element (thus modifying each value):

   foreach ($my_array as &$my_value) {
       $my_value += 42;
   }
   

   If you don't use &$my_value, then the addition won't have any effect on $my_array. But you could write the same not using references:

   foreach($my_array as $key=>$value) {
       $my_array[$key] = $value + 42;
   }
   

   The difference is that we are accessing/changing the original value directly with $my_array[$key].

DEMO