At the time of any new version release:
- some extensions can get removed
- some extensions or functionalities can get deprecated
- some other functionalities can get altered
The term ‘Deprecation’ here, implies that the programmers are offered a better alternative of a particular extension or a function so that its use is discouraged and in the future releases, this function or extension can be completely removed.
This necessitates the use of the migration document at the time of upgrading to a newer version. This document may cover the following:
- New features and functions
- Deprecated features and functions
- Changed features and functions
- Backward incompatible changes
- New global constants
- New classes and Interfaces
- Changes in SAPI modules
- Removed Extensions and SAPIs
- Other Changes
Here are the steps that we can follow while upgrading to PHP 7 from its older version:
The first thing that needs to be done is to eliminate the se of the removed extensions. The PHP migration document can offer quite a few alternatives for these removed extensions.
At the time of introducing PHP 7, the following are the extensions that have been removed:
Secondly, from the migration document we have the required information on which all functions have been changed. At the time of introducing a new version, some changes can also be introduced, such as:
- change in the return type
- removal of some of the parameters
So, we need to check in case any of these changed functions are in use on our PHP website, we need to refer to the migration document for these and make the required changes accordingly.
In case of PHP 7, some of the changed functions are as follows:
- The functions mktime() and gmmktime() do not accept is_dst parameter anymore.
- The functions substr() and iconv_substr() return an empty string now, where string is equivalent to start characters long
The third thing that needs to be done is an attempt to eliminate the use of deprecated functions and extensions as these will eventually get removed in the future releases.
In case of PHP 7, here are some of the features that are deprecated:
- PHP 4 style constructors – For creating constructors, PHP 4 used the same methods as the class they were defined in which is a deprecated feature and shall be removed in the future. So, these method names now need to get replaced by __construct()
- The static calls to non-static methods have also been deprecated and will be removed in the future releases
- The salt option for the password_hash() function has been deprecated since the function can generate a cryptographically secure salt in case the developer does not provide the salt.
The next i.e. the fourth thing that needs to be done is the treatment of the backward incompatible changes. At the time of introducing the new version, the migration document needs to be referred to for the ‘backward incompatible changes’.
Here are some of the backward incompatible changes:
- foreach does not change the internal array pointer anymore
- global now accepts only simple variables
- The variable variables cannot be used with the global keyword anymore.
- Hexadecimal strings are not considered numeric anymore
?> The output of the example mentioned above in PHP 7 is:bool(false)
- Changes to Division By Zero
Earlier, when 0 was used as the divisor for either the divide(/) or modulus(%) operators, and E_WARNING would be emitted and false would be returned. It has now changed to the divide operator returning a float as either +INF, -INF, or NAN. The modulus operator E_WARNING has been removed and will throw a DivisionByZeroError exception.
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