Page 229 - Beginning PHP 5.3

Chapter 8: Objects
echo “ < p > The letter ‘e’ occurs at position: “ . $myString- > strpos( “e” ) .
“ < /p > ”;
$myString- > madeUpMethod();

The first two method calls, $myString - > strlen() and $myString - > strtoupper() , don ’ t have any

arguments because their equivalent PHP functions only require one argument — the string to work
with — and this is automatically populated with the stored string thanks to the __call() method.
The third method call, $myString - > strpos( “ e ” ) , requires a single argument — the string to

search for — which is then passed as the second argument to PHP ’ s strpos() function.
The following table shows how the CleverString method calls map to the actual PHP
string functions:

M ethod C all PHP S tring F unction C all

$myString - > strlen() strlen( $this - > _theString )

$myString - > strtoupper() strtoupper( $this - > _theString )

$myString - > strpos( “ e ” ) strpos( $this - > _theString, “ e ” )

Finally, the script attempts to call a disallowed — in fact, nonexistent — string function, which
displays an error message in the page:

$myString-> madeUpMethod();

This example shows how easy it is to wrap a set of existing functions, methods, or API calls in a class
using a single __call() method. You could easily extend this example to allow practically all of
PHP ’ s tens of string functions to be called, without having to write much extra code.

Other Overloading Methods

Although you probably won ’ t use them much, it ’ s worth mentioning three other overloading methods
provided by PHP:

__isset() is called whenever the calling code attempts to call PHP ’ s isset() function on an invisible
property. It takes one argument — the property name — and should return true if the property is
deemed to be “ set, ” and false otherwise:
class MyClass {

public function __isset( $propertyName ) {
// All properties beginning with “test” are “set”
return ( substr( $propertyName, 0, 4 ) == “test” ) ? true : false;
}
}

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