PHP Programming Language - Cultural View

PHP Programming Language - Cultural View PHP Programming Language - Cultural View

culturalview.com
from culturalview.com More from this publisher
10.02.2013 Views

PHP syntax and semantics 170 ?> PHP supports quasi-anonymous functions through the create_function() function. These are not true anonymous functions because anonymous functions are nameless but functions can only be referenced by name in PHP. As of version 5.3, PHP also supports anonymous functions. [12] Function calls may be made via variables, where the value of a variable contains the name of the function to call. This is illustrated in the following example: PHP does not support named parameters or parameter skipping. [13] Some core PHP developers have publicly expressed disappointment with this decision. [13] . Others have suggested workarounds for this limitation. [14] Objects Basic object-oriented programming functionality was added in PHP 3. [15] Object handling was completely rewritten for PHP 5, expanding the feature set and enhancing performance. [16] In previous versions of PHP, objects were handled like primitive types. [16] The drawback of this method was that the whole object was copied when a variable was assigned or passed as a parameter to a method. In the new approach, objects are referenced by handle, and not by value. PHP 5 introduced private and protected member variables and methods, along with abstract classes and final classes as well as abstract methods and final methods. It also introduced a standard way of declaring constructors and destructors, similar to that of other object-oriented languages such as C++, and a standard exception handling model. Furthermore PHP 5 added Interfaces and allows for multiple Interfaces to be implemented. There are special interfaces that allow objects to interact with the runtime system. Objects implementing ArrayAccess can be used with array syntax and objects implementing Iterator or IteratorAggregate can be used with the foreach language construct. The static method and class variable features in Zend Engine 2 do not work the way some would expect. There is no virtual table feature in the engine, so static variables are bound with a name instead of a reference at compile time. [17] This example shows how to define a class, foo, that inherits from class bar. The function mystaticfunc is a public static function that can be called with foo::mystaticfunc();. class foo extends bar { function construct()

PHP syntax and semantics 171 } { $doo = "wah dee dee"; } public static function mystaticfunc() { $dee = "dee dee dum"; } If the developer creates a copy of an object using the reserved word clone, the Zend engine will check if a clone() method has been defined or not. If not, it will call a default clone() which will copy the object's properties. If a clone() method is defined, then it will be responsible for setting the necessary properties in the created object. For convenience, the engine will supply a function that imports the properties of the source object, so that the programmer can start with a by-value replica of the source object and only override properties that need to be changed. [18] References [1] Bray, Tim; et al (26 November 2008). "Processing Instructions" (http://www.w3.org/TR/2008/REC-xml-20081126/#sec-pi). Extensible Markup Language (XML) 1.0 (Fifth Edition). W3C. . Retrieved 2009-06-18. [2] "PHP: Basic syntax" (http://www.php.net/manual/en/language.basic-syntax.php). The PHP Group. . Retrieved 2008-02-22. [3] "Your first PHP-enabled page" (http://ca3.php.net/manual/en/tutorial.firstpage.php). The PHP Group. . Retrieved 2008-02-25. [4] "Variables" (http://www.php.net/manual/en/language.variables.php). The PHP Group. . Retrieved 2008-03-16. [5] "Instruction separation" (http://www.php.net/basic-syntax.instruction-separation). The PHP Group. . Retrieved 2008-03-16. [6] "Comments" (http://ca3.php.net/manual/en/language.basic-syntax.comments.php). The PHP Group. . Retrieved 2008-03-16. [7] "print" (http://www.php.net/print). The PHP Group. . Retrieved 2008-03-16. [8] "Hello World" (http://php.codenewbie.com/articles/php/1485/Hello_World-Page_1.html). Code Newbie. . Retrieved 2008-02-25. [9] "Colon Syntax in PHP" (http://www.kwista.com/programming/colon-syntax-in-php/). Kwista, LLC.. . Retrieved 2010-04-19. [10] "Alternative syntax for control structures" (http://php.net/manual/en/control-structures.alternative-syntax.php). The PHP Group. . Retrieved 2010-04-16. [11] "Types" (http://www.php.net/manual/en/language.types.php). The PHP Group. . Retrieved 2008-03-16. [12] "Functions" (http://www.php.net/manual/en/language.functions.php). The PHP Group. . Retrieved 2008-03-16. [13] "PHP 6 Dropped Items" (http://wiki.php.net/todo/backlog#dropped_items). The PHP Group. . Retrieved 2009-01-09. [14] "PHP Skipped and Named Parameters" (http://www.seoegghead.com/software/php-parameter-skipping-and-named-parameters.seo). SEO Egghead Inc.. . Retrieved 2009-01-09. [15] "History of PHP and related projects" (http://www.php.net/history). The PHP Group. . Retrieved 2008-02-25. [16] "PHP 5 Object References" (http://mjtsai.com/blog/2004/07/15/php-5-object-references/). mjtsai. . Retrieved 2008-03-16. [17] "Classes and Objects (PHP 5)" (http://ca3.php.net/zend-engine-2.php). The PHP Group. . Retrieved 2008-03-16. [18] "Object cloning" (http://ca3.php.net/language.oop5.cloning). The PHP Group. . Retrieved 2008-03-16.

<strong>PHP</strong> syntax and semantics 170<br />

?><br />

<strong>PHP</strong> supports quasi-anonymous functions through the create_function() function. These are not true anonymous<br />

functions because anonymous functions are nameless but functions can only be referenced by name in <strong>PHP</strong>. As of<br />

version 5.3, <strong>PHP</strong> also supports anonymous functions. [12]<br />

Function calls may be made via variables, where the value of a variable contains the name of the function to call.<br />

This is illustrated in the following example:<br />

<br />

<strong>PHP</strong> does not support named parameters or parameter skipping. [13] Some core <strong>PHP</strong> developers have publicly<br />

expressed disappointment with this decision. [13] . Others have suggested workarounds for this limitation. [14]<br />

Objects<br />

Basic object-oriented programming functionality was added in <strong>PHP</strong> 3. [15] Object handling was completely rewritten<br />

for <strong>PHP</strong> 5, expanding the feature set and enhancing performance. [16] In previous versions of <strong>PHP</strong>, objects were<br />

handled like primitive types. [16] The drawback of this method was that the whole object was copied when a variable<br />

was assigned or passed as a parameter to a method. In the new approach, objects are referenced by handle, and not<br />

by value. <strong>PHP</strong> 5 introduced private and protected member variables and methods, along with abstract classes and<br />

final classes as well as abstract methods and final methods. It also introduced a standard way of declaring<br />

constructors and destructors, similar to that of other object-oriented languages such as C++, and a standard exception<br />

handling model. Furthermore <strong>PHP</strong> 5 added Interfaces and allows for multiple Interfaces to be implemented. There<br />

are special interfaces that allow objects to interact with the runtime system. Objects implementing ArrayAccess can<br />

be used with array syntax and objects implementing Iterator or IteratorAggregate can be used with the foreach<br />

language construct. The static method and class variable features in Zend Engine 2 do not work the way some would<br />

expect. There is no virtual table feature in the engine, so static variables are bound with a name instead of a reference<br />

at compile time. [17]<br />

This example shows how to define a class, foo, that inherits from class bar. The function mystaticfunc is a<br />

public static function that can be called with foo::mystaticfunc();.<br />

class foo extends bar<br />

{<br />

function construct()

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!