PHP in a Nutshell

Copying Objects

From PHP 5 onward, objects are always handled as references. This means that when you pass an object into a function, any changes you make to it in there are reflected outside the function. For example:

    function namechange($dog) {
            $dog->Name = 'Dozer';
    }

    namechange($poppy);
    print $poppy->Name . "\n";

Here we define a function that accepts one variable, $dog, then changes its name to Dozer. We then pass our $poppy dog into the function, and output its name—unsurprisingly, it outputs "Dozer" rather than "Poppy". Sometimes it is important to only work on copies of objects, particularly if you don't want to affect the state of the original. To do this, we use the built-in keyword clone, which performs a complete copy of the object. For example, we could use the namechange() function above like this:

    namechange(clone $poppy);

That would create a copy of $poppy and pass it into namechange(), leaving the original $poppy untouched. Here is the output of the code now:

    Creating Poppy
    Creating a poodle
    My name is Poppy. If you find me, please call 555-1234
    Dozer is no more...
    Poppy
    Poppy is no more...

Note that Dozer is still mentioned—that is because the copied object passed into namechange() gets its name changed to Dozer; then, when the function ends, the copied object is automatically destroyed by PHP, and its destructor is called. However, $poppy lives on untouched, as you can see from the last two lines.

Internally, the clone keyword copies all the properties from the ...