There is a feature in PHP that allows to embed data (including binary data) into PHP scripts and it are not parsed by PHP interpreter. It is diferent from exit instruction, that stops script execution, but does not stop the PHP parser. The feature is provided by "__halt_compiler" instruction, that ignores all data after the point it was called.
PHP is an HTML embedded language. This means the PHP code can be inside an HTML, but should have one way to determine whether a stretch of code is PHP or HTML. The way is the use of PHP delimiters. The PHP interpreter is applicable to the stretch of code delimited by the PHP delimiters.
Some programmers use PHP code delimiters, but they do not know about their nuances. Let's see them at this post.
Although I like and encourage the use of PHP, I do not like one of its most significant feature: the fact that the language is HTML embedded. It is the language has code delimiter and all code behind the delimiter is considered text blocks, which are sent directly to the standard output (often it is an HTML code).
Data Warehouse is a computer system that keeps organization data. Since sectors names until operational data. For example, in a university system, the data warehouse provides classes informations (avaliations, students, professors), it is the operational level of any university.
With PHP, you can implement a code of a software that can create another code. It is simple, because a PHP script is a text file.
Although, the language allows you to create a script that modify its own behavior at execution time. It can be useful to optimize stretch of code. This feature is based on "eval" PHP function.