The operator = used in PHP has two different functions:
1. Add:
$value = 3;
$value += 5;
//$value = 8
2. Setting default values in an array:
$arr = array('foo' => true);
$arr += array('foo' => false);
//$arr = array('foo' => true)
As the key “foo” is already defined in the array, it does not change. On the other hand:
$arr = array();
$arr += array('foo' => false);
//$arr = array('foo' => false)
Here the pair 'foo' => false"
is created by default in $arr
.