Zend PHP5 certification Exam study review 7: PHP4 And PHP5

Due to the fact that many hosting providers and live web sites are still using PHP4, and this situation is likely remaining for some time; the PHP5 Certification Exam has a topic on the difference between PHP4 and PHP5. You should have very good knowing that PHP5 has great improvement on which subject as well as deprecations on older code. I did post review on the Language Basic and Function topics in the exam, because I think these topic is too “basic” to write out and you should quickly or already know them. However, this post do start with some basic concept then migrating to the difference made in PHP5 as compare to older version; because I think this post is consider the “Language Level” subjects on PHP. So, here comes “what exactly language construct”…
PHP language construct

The “exact” definition for “Language Construct”.

It’s kind of like the “core language definition” of things such as: if (…) while (…) <?php and ?> and so on In PHP, a handful of common things that many beginners *THINK* are functions are actually Language Constructs: require include echo isset I belive most of them are documented as such in the manual now. Language Construct roughly corresponds to the “grammar” of the language, if you will.

This means that they are integral part of the language, just like ‘if’, or any operator +, *, etc, though they look pretty much like functions. It means that though syntactically they look a functions and in the manual they are listed under functions, this is only to make them easy to use, understand and locate in the documentation. That is why certain rules for functions can be relaxed, such as requiring parenthesis around its arguments, which are not actually needed but are there so that they have the same look as regular functions.

Language Features
PHP 5 allows limited type hinting. This allows you to specify that the parameter to a function or class method can only be of a specific class (or one of its subclasses), or an array. However, you may not specify any other scalar types.

The foreach construct now supports by-reference declaration of the value element.

A number of new functions, particularly for string and array manipulation, has also been added to the core platform.

OOP
For all intents and purposes, all objects in PHP 5 are passed by reference. This means that assigning an object to a variable will not create a copy of the former, but simply creates another reference to it.

Constants, as well as static methods and properties, can now be defined within the scope of a class.

Class methods and properties now feature visibility, and can be declared as public, private or protected. Classes and methods can also be declared as final to prevent further inheritance.

Since all objects are assigned by reference, you now need a specialized mechanism to copy objects. This is provided by the clone construct and the __clone() magic method.

PHP 5 features unified constructors and destructors—all constructors should now be named __construct(), and the new __destruct() magic method has been added for object destruction.

With the addition of interfaces and abstract classes, PHP developers now have far greater control over how they implement their object-oriented code. Interfaces can be used to define common APIs, while abstract classes provide models for class implementations that follow a specific blueprint.

Class definitions can now be loaded on demand by using the __autoload() function.

Magic Methods
A multitude of new “magic” methods has been introduced in PHP 5:

.__get() and __set() are called when accessing or assigning an undefined object property, while __call() is executed when calling a non-existent method of a class.

.__isset() is called when passing an undefined property to the isset() construct.

.__unset() is called when passing an undefined property to unset().

.__toString() is called when trying to directly echo or print() an object.

.__set_state() is inserted dynamically by var_export() to allow for reinitialization on execution of var_export()’s output.

Selected New Extensions
.SimpleXML allows easy access to XML data using object and array notation.

.PHP 5 also introduces a DOMXML, DOMXSL and Sablotron replacement in the form of the libxml2-based DOM and XSL extensions.

.The PHP Data Objects (PDO) extension provides a unified database access extension that allows access to many different types of database systems by using a common interface. PDO is not an abstraction layer—except for prepared queries, it does nothing to abstract the actual database code (SQL), itself.

.The hash extension is a new replacement for the GPLed libmhash; it was added to the PHP core starting with version 5.1.2. It can produce hashes using many algorithms, including the familiar MD5and SHA1, aswell as some more secure (albeit slower) algorithms, such as snefru.

.The Standard PHP Library (SPL) provides numerous interfaces that enhance the way classes interact with the PHP language, including the new Iterator interfaces.

.The new Reflection extension allows for runtime introspection of executing PHP code.

Error Management
.Classes now support exceptions; the new set_exception_handler() function allows you to define a script-wide exception handler.

.The E_STRICT error reporting level has been added to the language to emit notices when legacy or deprecated code is encountered.

.Not included in E_ALL:
– Non static method calls
– By reference issues
– var key word

Conclusion:

. ByRef rather than copying
. $myClone = clone $original;
. __clone() function called on clone if it exists
. Constructor and Destructor
. Magic Methods (in OO Section)
. Class constants
. SimpleXML
. PDO
. SPL
. instanceOf
. Type hinting

Objects got better, faster
The way we handled objects got better
E_STRICT is available, it’s not included in E_ALL

16 Comments - Leave a comment
  1. Heena says:

    hi,

    i got lots of information for zend certification. its very helpful… i have one question if can help me.

    consider the following code block.
    <?
    function &myfun(){
    $str = “mystr”;
    var_dump($str);
    return ($undefined);
    }
    echo “”;
    for($i=0;$i none of the above
    2> this could would cause an automatic segmentation fault in php4
    3> this code would throw a syntax error in php4
    4> returning an undefined variable by reference in php4 would cause eventual memory corruption
    5> you could not return undefined variable by reference in php4

    what could be the answer?

    please help
    thanks

  2. Heena says:

    <?
    function &myfun(){
    $str = “mystr”;
    var_dump($str);
    return ($undefined);
    }
    echo “”;
    for($i=0;$i

  3. Heena says:

    hey i can not post the code?

  4. Heena says:

    less than 10;$i++){
    $retval = myfun();
    }
    ?>

  5. David Adam says:

    Hi,
    First, I am sorry if the for($i=0; $i<10;$i++)…

  6. David Adam says:

    had the problem. But, to me it seems fine.

    As to the question, I think the answer is 4).

    This code in PHP5 is definitely cause an error. But, in PHP4, there seems some problem found on “return by reference” in the language itself.

  7. Heena says:

    Consider the following php4 code:

    what if any potential compatibility problems will this conditional have in php5?
    1>this code is undefined in php4
    2>none of above
    3>$obj1 and $obj2 musr have the same property values in php5
    4>$obj1 and $obj2 must be the same instance in php5
    5>there are no compatibility issues
    please answer
    thanks

  8. Heena says:

    hey there might be some problem i cant post php code

  9. David Adam says:

    Do you mean post the code containing the php tags: < ?php and ?>?

  10. Heena says:

    yes I tried to post with tag… btw code is here
    if($obj1===$obj2){
    //do something
    }

  11. David Adam says:

    The answer is 4>$obj1 and $obj2 must be the same instance in php5.

  12. mcloide says:

    Hi Heena, about the first question, the correct answer would be 3. PHP4 will throw a notice error for using an undefined variable.

  13. Henry Lu says:

    I agree mcloide for the following reasons:
    You should never use parentheses around your return variable when returning by reference, as this will not work. You can only return variables by reference, not the result of a statement. If you use return ($a); then you’re not returning a variable, but the result of the expression ($a) (which is, of course, the value of $a).
    If you are attempting to return the result of an expression, and not a variable, by reference. You can only return variables by reference from a function – nothing else. Since PHP 4.4.0 in the PHP4 branch, and PHP 5.1.0 in the PHP5 branch, an E_NOTICE error is issued if the code tries to return a dynamic expression or a result of the new operator.

  14. kleo says:

    E_ALL includes E_STRICT in 5.4.0 and up

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