Backward Incompatible Changes
Although most existing PHP 4 code should work without changes, you should pay attention to the following backward incompatible changes:
- There are some new reserved keywords.
- strrpos() and strripos() now use the entire string as a needle.
- Illegal use of string offsets causes E_ERROR instead of E_WARNING. An example illegal use is: $str = 'abc'; unset($str[0]);.
- array_merge() was changed to accept only arrays. If a non-array variable is passed, a E_WARNING will be thrown for every such parameter. Be careful because your code may start emitting E_WARNING out of the blue.
- PATH_TRANSLATED server variable is no longer set implicitly under Apache2 SAPI in contrast to the situation in PHP 4, where it is set to the same value as the SCRIPT_FILENAME server variable when it is not populated by Apache. This change was made to comply with the » CGI specification. see also the $_SERVER['PATH_TRANSLATED'] description in the manual. This issue also affects PHP versions >= 4.3.2.
- The T_ML_COMMENT constant is no longer defined by the Tokenizer extension. If error_reporting is set to E_ALL, PHP will generate a notice. Although the T_ML_COMMENT was never used at all, it was defined in PHP 4. In both PHP 4 and PHP 5 // and /* */ are resolved as the T_COMMENT constant. However the PHPDoc style comments /** */, which starting PHP 5 are parsed by PHP, are recognized as T_DOC_COMMENT.
- $_SERVER should be populated with argc and argv if variables_order includes "S". If you have specifically configured your system to not create $_SERVER, then of course it shouldn't be there. The change was to always make argc and argv available in the CLI version regardless of the variables_order setting. As in, the CLI version will now always populate the global $argc and $argv variables.
- An object with no properties is no longer considered "empty".
- In some cases classes must be declared before use. It only happens if some of the new features of PHP 5 (such as interfaces) are used. Otherwise the behaviour is the old.
- get_class(), get_parent_class() and get_class_methods() now return the name of the classes/methods as they were declared (case-sensitive) which may lead to problems in older scripts that rely on the previous behaviour (the class/method name was always returned lowercased). A possible solution is to search for those functions in all your scripts and use strtolower(). This case sensitivity change also applies to the magical predefined constants __CLASS__, __METHOD__, and __FUNCTION__. The values are returned exactly as they're declared (case-sensitive).
- ip2long() now returns FALSE when an invalid IP address is passed as argument to the function, and no longer -1.
- If there are functions defined in the included file, they can be used in the main file independent if they are before return() or after. If the file is included twice, PHP 5 issues fatal error because functions were already declared, while PHP 4 doesn't complain about it. It is recommended to use include_once() instead of checking if the file was already included and conditionally return inside the included file.
- include_once() and require_once() first normalize the path of included file on Windows so that including A.php and a.php include the file just once.
- Passing an array to a function by value no longer resets the array's internal pointer for array accesses made within the function. In other words, in PHP 4 when you passed an array to a function, its internal pointer inside the function would be reset, while in PHP 5, when you pass an array to a function, its array pointer within the function will be wherever it was when the array was passed to the function.
New Functions
In PHP 5 there are some new functions. Here is the list of them:
- array_combine() – Creates an array by using one array for keys and another for its values
- array_diff_uassoc() – Computes the difference of arrays with additional index check which is performed by a user supplied callback function
- array_udiff() – Computes the difference of arrays by using a callback function for data comparison
- array_udiff_assoc() – Computes the difference of arrays with additional index check. The data is compared by using a callback function
- array_udiff_uassoc() – Computes the difference of arrays with additional index check. The data is compared by using a callback function. The index check is done by a callback function also
- array_walk_recursive() – Apply a user function recursively to every member of an array
- array_uintersect_assoc() – Computes the intersection of arrays with additional index check. The data is compared by using a callback function
- array_uintersect_uassoc() – Computes the intersection of arrays with additional index check. Both the data and the indexes are compared by using separate callback functions
- array_uintersect() – Computes the intersection of arrays. The data is compared by using a callback function
- ibase_affected_rows() – Return the number of rows that were affected by the previous query
- ibase_backup() – Initiates a backup task in the service manager and returns immediately
- ibase_commit_ret() – Commit a transaction without closing it
- ibase_db_info() – Request statistics about a database
- ibase_drop_db() – Drops a database
- ibase_errcode() – Return an error code
- ibase_free_event_handler() – Cancels a registered event handler
- ibase_gen_id() – Increments the named generator and returns its new value
- ibase_maintain_db() – Execute a maintenance command on the database server
- ibase_name_result() – Assigns a name to a result set
- ibase_num_params() – Return the number of parameters in a prepared query
- ibase_param_info() – Return information about a parameter in a prepared query
- ibase_restore() – Initiates a restore task in the service manager and returns immediately
- ibase_rollback_ret() – Rollback transaction and retain the transaction context
- ibase_server_info() – Request statistics about a database server
- ibase_service_attach() – Connect to the service manager
- ibase_service_detach() – Disconnect from the service manager
- ibase_set_event_handler() – Register a callback function to be called when events are posted
- ibase_wait_event() – Wait for an event to be posted by the database
- iconv_mime_decode() – Decodes a MIME header field
- iconv_mime_decode_headers() – Decodes multiple MIME header fields at once
- iconv_mime_encode() – Composes a MIME header field
- iconv_strlen() – Returns the character count of string
- iconv_strpos() – Finds position of first occurrence of a needle within a haystack
- iconv_strrpos() – Finds the last occurrence of a needle within a haystack
- iconv_substr() – Cut out part of a string
- stream_copy_to_stream() – Copies data from one stream to another
- stream_get_line() – Gets line from stream resource up to a given delimiter
- stream_socket_accept() – Accept a connection on a socket created by stream_socket_server()
- stream_socket_client() – Open Internet or Unix domain socket connection
- stream_socket_get_name() – Retrieve the name of the local or remote sockets
- stream_socket_recvfrom() – Receives data from a socket, connected or not
- stream_socket_sendto() – Sends a message to a socket, whether it is connected or not
- stream_socket_server() – Create an Internet or Unix domain server socket
- idate() – Format a local time/date as integer
- date_sunset() – Time of sunset for a given day and location
- date_sunrise() – Time of sunrise for a given day and location
- time_nanosleep() – Delay for a number of seconds and nanoseconds
- str_split() – Convert a string to an array
- strpbrk() – Search a string for any of a set of characters
- substr_compare() – Binary safe optionally case insensitive comparison of two strings from an offset, up to length characters
Other:
- convert_uudecode() – decode a uuencoded string
- convert_uuencode() – uuencode a string
- curl_copy_handle() – Copy a cURL handle along with all of its preferences
- dba_key_split() – Splits a key in string representation into array representation
- dbase_get_header_info() – Get the header info of a dBase database
- dbx_fetch_row() – Fetches rows from a query-result that had the DBX_RESULT_UNBUFFERED flag set
- fbsql_set_password() – Change the password for a given user
- file_put_contents() – Write a string to a file
- ftp_alloc() – Allocates space for a file to be uploaded
- get_declared_interfaces() – Returns an array of all declared interfaces
- get_headers() – Fetches all the headers sent by the server in response to a HTTP request
- headers_list() – Returns a list of response headers sent (or ready to send)
- http_build_query() – Generate URL-encoded query string
- image_type_to_extension() – Get file extension for image-type returned by getimagesize(), exif_read_data(), exif_thumbnail(), exif_imagetype()
- imagefilter() – Applies a filter to an image using custom arguments
- imap_getacl() – Gets the ACL for a given mailbox
- ldap_sasl_bind() – Bind to LDAP directory using SASL
- mb_list_encodings() – Returns an array of all supported encodings
- pcntl_getpriority() – Get the priority of any process
- pcntl_wait() – Waits on or returns the status of a forked child as defined by the waitpid() system call
- pg_version() – Returns an array with client, protocol and server version (when available)
- php_check_syntax() – Check the syntax of the specified file
- php_strip_whitespace() – Return source with stripped comments and whitespace
- proc_nice() – Change the priority of the current process
- pspell_config_data_dir() – Change location of language data files
- pspell_config_dict_dir() – Change location of the main word list
- setrawcookie() – Send a cookie without URL-encoding the value
- scandir() – List files and directories inside the specified path
- snmp_read_mib() – Reads and parses a MIB file into the active MIB tree
- sqlite_fetch_column_types() – Return an array of column types from a particular table
New Object Model
In PHP 5 there is a new Object Model. PHP's handling of objects has been completely rewritten, allowing for better performance and more features. In previous versions of PHP, objects were handled like primitive types (for instance integers and strings). The drawback of this method was that semantically 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 (one can think of a handle as an object's identifier).
Many PHP programmers aren't even aware of the copying quirks of the old object model and, therefore, the majority of PHP applications will work out of the box, or with very few modifications.
The new Object Model is documented at the Language Reference.
In PHP 5, function with the name of a class is called as a constructor only if defined in the same class. In PHP 4, it is called also if defined in the parent class.
See also the zend.ze1_compatibility_mode directive for compatability with PHP 4.
Passed by Reference
This is an important change. In PHP4, everything was passed by value, including objects. This has changed in PHP5 — all objects are now passed by reference.
PHP Code:
$joe = new Person();
$joe->sex = 'male';
$betty = $joe;
$betty->sex = 'female';
echo $joe->sex; // Will be 'female'
The above code fragment was common in PHP4. If you needed to duplicate an object, you simply copied it by assigning it to another variable. But in PHP5 you must use the new clone keyword.
Note that this also means you can stop using the reference operator (&). It was common practice to pass your objects around using the & operator to get around the annoying pass-by-value functionality in PHP4.
Class Constants and Static Methods/Properties
You can now create class constants that act much the same was as define()'ed constants, but are contained within a class definition and accessed with the :: operator.
Static methods and properties are also available. When you declare a class member as static, then it makes that member accessible (through the :: operator) without an instance. (Note this means within methods, the $this variable is not available)
Visibility
Class methods and properties now have visibility. PHP has 3 levels of visibility:
1. Public is the most visible, making methods accessible to everyone and properties readable and writable by everyone.
2. Protected makes members accessible to the class itself and any subclasses as well as any parent classes.
3. Private makes members only available to the class itself.
Unified Constructors and Destructors
PHP5 introduces a new unified constructor/destructor names. In PHP4, a constructor was simply a method that had the same name as the class itself. This caused some headaches since if you changed the name of the class, you would have to go through and change every occurrence of that name.
In PHP5, all constructors are named __construct(). That is, the word construct prefixed by two underscores. Other then this name change, a constructor works the same way.
Also, the newly added __destruct() (destruct prefixed by two underscores) allows you to write code that will be executed when the object is destroyed.
Abstract Classes
PHP5 lets you declare a class as abstract. An abstract class cannot itself be instantiated, it is purely used to define a model where other classes extend. You must declare a class abstract if it contains any abstract methods. Any methods marked as abstract must be defined within any classes that extend the class. Note that you can also include full method definitions within an abstract class along with any abstract methods.
Interfaces
PHP5 introduces interfaces to help you design common APIs. An interface defines the methods a class must implement. Note that all the methods defined in an interface must be public. An interface is not designed as a blueprint for classes, but just a way to standardize a common API.
The one big advantage to using interfaces is that a class can implement any number of them. You can still only extend on parent class, but you can implement an unlimited number of interfaces.
Magic Methods
There are a number of "magic methods" that add an assortment to functionality to your classes. Note that PHP reserves the naming of methods prefixed with a double-underscore. Never name any of your methods with this naming scheme!
Some magic methods to take note of are __call, __get, __set and __toString. These are the ones I find most useful.
Finality
You can now use the final keyword to indicate that a method cannot be overridden by a child. You can also declare an entire class as final which prevents it from having any children at all.
Error Reporting
As of PHP 5 the error reporting constant E_STRICT is available, with the value 2048. When enabled, messages will be issued to warn you about code usage which is deprecated or which may not be future-proof.
Exceptions
PHP finally introduces exceptions! An exception is basically an error. By using an exception however, you gain more control the simple trigger_error notices we were stuck with before.
An exception is just an object. When an error occurs, you throw an exception. When an exception is thrown, the rest of the PHP code following will not be executed. When you are about to perform something "risky", surround your code with a try block. If an exception is thrown, then your following catch block is there to intercept the error and handle it accordingly. If there is no catch block, a fatal error occurs.
PHP Code:
try {
$cache->write();
} catch (AccessDeniedException $e) {
die('Could not write the cache, access denied.');
} catch (Exception $e) {
die('An unknown error occurred: ' . $e->getMessage());
}
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Difference between Php4 and Php5 – Aditya Didwania
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Difference between Php4 and Php5 – Aditya Didwania
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Difference between Php4 and Php5 – Aditya Didwania
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Difference between Php4 and Php5 – Aditya Didwania
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