There are many differences between PHP 5 and 7. Some of the main points are:
Performance: it is obvious that later versions are always better than the previous versions if they are stable. So, if you execute code in both versions, you will find the performance of PHP 7 is better than PHP5. This is because PHP 5 use Zend II and PHP & uses the latest model PHP-NG or Next Generation.
Return Type: In PHP 5, the programmer is not allowed to define the type of return value of a function which is the major drawback. But in PHP 7, this limitation is overcome and a programmer is allowed to define the return type of any function.
Error handling: In PHP 5, there is high difficulty to manage fatal errors but in PHP 7, some major errors are replaced by exceptions which can be managed effortlessly. In PHP 7, the new engine Exception Objects has been introduced.
64-bit support: PHP 5 doesn’t support 64-bit integer while PHP 7 supports native 64-bit integers as well as large files.
Anonymous Class: Anonymous class is not present n PHP 5 but present in PHP 7. It is basically used when you need to execute the class only once to increase the execution time.
New Operators: Some new operators have added in PHP 7 such as <=> which is called a three-way comparison operator. Another operator has added is a null coalescing operator which symbol as?? and use to find whether something exists or not.
Group Use declaration: PHP 7 includes this feature whereas PHP 5 doesn’t have this feature.