Mastering PHP 7

Objects and references

There are two ways to pass arguments within the code:

• By reference: This is where both the caller and callee use the same variable for argument.
• By value: This is where both the caller and callee have their own copy of the variable for argument. If the callee decides to change the value of the passed argument, the caller would not notice it.

by value is the default PHP behavior, as shown in the following example:

<?phpclass Util{  function hello($msg)  {    $msg = "<p>Welcome $msg</p>";    return $msg;  }}$str = 'John';$obj = new Util();echo $obj->hello($str); // Welcome Johnecho $str; // John

Looking at the internals of the hello() method, we can see it is resetting the $msg argument value to another string value wrapped ...