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12. Object Oriented Features - public, private, protected

PHP scripting language provides object oriented features through the class keyword. Features like public, private and protected will be supported in the future release (they are in TODO list). In the meantime, you can use the following coding conventions to distinguish between private, public and protected variables:

1. All private variables and functions always start with underscore "_" followed by lowercase letters like var $_myvar;

2. All Protected variables and functions always start with "_T" followed by lowercase letters like var $_Tmyvar;

3. All Public variables and functions do not start with underscore "_" like var $myvar;

4. All variables and functions always start with lowercase letter (no uppercase) like var $_myvar; and NOT like var $_Myvar;

class someabc {
        var $_conn;                     // Private variable
        var $_Tmyvar;                   // Protected variable
        var $connMYCONNECTION;          // Public variable
        var $connToDb;                  // Public variable
        var $myvar3;                    // Public variable
        var $myvarTHISTEST;             // Public variable

        function _foofunction() {}      // Private function
        function _Tfoofunction() {}     // Protected function
        function foofunction() {}       // Public function
}

The private, protected declarations provide the encapsulation and data-hiding. But you must consider the following disadvantages of encapsulation:

• Encapsulation usually requires more code, hence it sacrifices performance especially for scripting languages like PHP

• Encapsulation requires lots of Set/Get methods for private/protected properties.

• Since encapsulation unneccessarily increases the code size, it is not recommended for scripting language like PHP.

• You can enforce a good degree of encapsulation by using the coding convention suggested in this section.