diff options
Diffstat (limited to 'Zend/ZEND_CHANGES')
| -rw-r--r-- | Zend/ZEND_CHANGES | 233 |
1 files changed, 0 insertions, 233 deletions
diff --git a/Zend/ZEND_CHANGES b/Zend/ZEND_CHANGES deleted file mode 100644 index 1570bd53c9..0000000000 --- a/Zend/ZEND_CHANGES +++ /dev/null @@ -1,233 +0,0 @@ -Changes in the Zend Engine 2.0 - - * New object model. - - The Zend Engine's handling of objects has been completely - changed in order to allow for new features, but also to increase - its performance. - - Objects were handled in previous versions like primitive types - (for instance integers and strings). The drawback of this method - is, that semantically the whole object was copied when a - variable was assigned or parameters were passed to a method. The - new approach refers to objects by handle and not by value (one - can think of a handle as an objects' ID). - - Many PHP programmers aren't even aware of the copying quirks of - the old object model and, therefore, there is a relatively good - chance that the amount of PHP applications that will work out of - the box or after a very small amount of modifications would be - high. - - To simplify migration, the Zend Engine 2.0 supports an optional - 'auto-clone' feature, which performs a cloning of the object - whenever it would have been copied in version 1.0. Optionally, - it emits an E_NOTICE message whenever such an automatic clone - occurs, in order to allow developers to gradually migrate to the - version 2.0-style behavior (without automatic clones). - - * delete statement. - - The Zend Engine 1.0 had no means to force deletion of an object - if there are still references to it. The newly introduces delete - statement calls the object’s destructor and frees it even if the - object is referenced by some other places in the engine. Other - references to the deleted object become stale and trying to - access them results in a fatal error. - - Note that if you have a user-defined function delete() in an old - script, this script will yield a parser error with the Zend - Engine 2.0, since 'delete' is now a reserved word. - - * Exceptions. - - The Zend Engine 1.0 had no exception handling. The Zend Engine 2.0 - introduces a exception model similar to that of other programming - languages. - - Example - - try { - code - - if (failure) { - throw new MyException(Failure); - } - - code - } catch ($exception) { - handle exception - - throw $exception; // Re-throw exception. - } - - Old code that does not use exceptions will run without - modifications. - - * Namespaces. - - The Zend Engine 1.0 provided only three scopes: the global - scope, the class scope and the function scope. All scopes but - classes could contain variables, only the class and global - scopes could contain functions, while only the global scope - could contain constants and classes. This means that all of the - Zend Engine 1.0's scoping methods were inherently limited for - solving symbol name collision problems. - - The Zend Engine 2.0 introduces the concept of namespaces to - manage the symbol collision problem by making it possible to - define multiple symbol tables able to contain all types of - symbols. The Zend Engine is aware of a current namespace, - defaulting to the current global one. The current namespace may - be changed on a file-by-file basis. Symbols in other namespaces - than the current one may be referenced using a new namespace - operator. It is possible to "import" symbols from one namespace - into another. - - Old code that does not take advantage of namespaces will run - without modifications. - -Changes in the Zend Engine 1.0 - - The Zend Engine was designed from the ground up for increased speed, - reduced memory consumption and more reliable execution. We dare say - it meets all of these goals and does so pretty well. Beyond that, - there are several improvements in the language engine features: - - * References support. - - $foo = &$a; would make $foo and $a be two names to the same - variable. This works with arrays as well, on either side; e.g., - $foo = &$a[7]; would make $foo and $a[7] be two names to the - same variable. Changing one would change the other and vice - versa. - - * Object overloading support. - - This feature allows various OO libraries to use the OO notation - of PHP to access their functionality. Right now, no use is made - of that feature, but we'd have a COM module ready by the time - PHP 4.0 is released. A CORBA module would probably follow. - - * include() and eval() are now functions, and not statements. - - That means they return a value. The default return value from - include() and eval() is 1, so that you can do if (include()) - without further coding. The return value may be changed by - returning a value from the global scope of the included file or - the evaluated string. For example, if 'return 7;' is executed in - the global scope of foo.inc, include("foo.inc") would evaluate - to 7. - - * Automatic resource deallocation. - - Several people have been bitten by the fact that PHP 3.0 had no - concept of reference counting. The Zend Engine adds full - reference counting for every value in the system, including - resources. As soon as a resource is no longer referenced from - any variable, it is automatically destroyed to save memory and - resources. The most obvious example for the advantage in this is - a loop that has an SQL query inside it, something like '$result - = sql_query(...);'. In PHP 3.0, every iteration resulted in - another SQL result-set allocated in the memory, and all of the - result sets weren't destroyed until the end of the script's - execution. With the Zend Engine, as soon as we overwrite an old - result set with a new one, the old result set which is no longer - referenced, is destroyed. - - * Full support for nesting arrays and objects within each other, - in as many levels as you want. - - * true and false are now constants of type boolean. - - Comparing any other value to them would convert that value to a - boolean first, and conduct the comparison later. That means, for - example, that 5==true would evaluate to true (in PHP 3.0, true - was nothing but a constant for the integer value of 1, so - 5==true was identical to 5==1, which was false). - - * Runtime binding of function names. - - This complex name has a simple explanation - you can now call - functions before they're declared! - - * Added here-docs support. - - * Added foreach. - - Two syntaxes supported: - - foreach(array_expr as $val) statement - foreach(array_expr as $key => $val) statement - - * A true unset() implementation. - - A variable or element that is unset(), is now sent to oblivion - in its entirely, no trace remains from it. - - * Output buffering support. - - Use ob_start() to begin output buffering, ob_end_flush() to end - buffering and send out the buffered contents, ob_end_clean() to - end buffering without sending the buffered contents, and - ob_get_contents() to retreive the current contents of the output - buffer. Header information (header(), content type, cookies) are - not buffered. By turning on output buffering, you can - effectively send header information all throughout your file, - regardless of whether you've emitted body output or not. - - * Full variable reference within quoted strings: - - ${expr} - full indirect reference support for scalar - variables - {variable} - full variable support - - For example: - - $foo[5]["bar"] = "foobar"; - print "{$foo[5]["bar"]}"; // would print "foobar" - - * Ability to call member functions of other classes from within - member functions or from the global scope. - - You can now, for example, override a parent function with a - child function, and call the parent function from it. - - * Runtime information for classes (class name, parent, available - functions, etc.). - - * Much more efficient syntax highlighter - runs much quicker, - performs more reliably, and generates much tighter HTML. - - * A full-featured debugger has been integrated with the language - (supports breakpoints, expression evaluation, step-in/over, - function call backtrace, and more). - - The Zend Engine claims 100% compatability with the engine of PHP - 3.0, and is shamelessly lying about it. Here's why: - - * Static variable initializers only accept scalar values - (in PHP 3.0 they accepted any valid expression). The impact - should be somewhere in between void and non existent, since - initializing a static variable with anything but a simple - static value makes no sense at all. - - * The scope of break and continue is local to that of an - include()'d file or an eval()'d string. The impact should - be somewhat smaller of the one above. - - * The return statement no longer works from a require()'d file. It - hardly worked in PHP 3.0, so the impact should be fairly small. If - you want this functionality - use include() instead. - - * unset() is no longer a function, but a statement. - - * The following letter combination is not supported within - encapsulated strings: "{$". If you have a string that includes - this letter combination, for example, print "{$somevar"; (which - printed the letter { and the contents of the variable $somevar in - PHP 3.0), it will result in a parse error with the Zend Engine. - In this case, you would have to change the code to print - "\{$somevar"; This incompatability is due to the full variable - reference within quoted strings feature added in the Zend - Engine. |