What are the PHP technologies?

1. Features of smarty template

Fast speed, compilation, caching technology, plug-in mechanism, powerful performance logic

2. PHP’s garbage collection mechanism

PHP can automatically manage memory and clear objects that are no longer needed.

PHP uses a simple garbage collection mechanism called reference counting. Each object contains a reference counter, and each reference connected to the object increases the counter by one. When reference leaves the living space or is set to NULL, the counter is decremented by 1. When an object's reference counter reaches zero, PHP knows that you no longer need to use the object and releases the memory space it occupies.

3. The difference between mysql_fetch_row() and mysql_fetch_array()

mysql_fetch_row() stores a column of the database in a zero-based array, the first column At index 0 of the array, the second column is at index 1, and so on. mysql_fetch_assoc() stores a column of the database in an associative array. The index of the array is the field name. For example, my database query returns the three fields "first_name", "last_name", and "email". The index of the array is "first_name". ”, “last_name” and “email”. mysql_fetch_array() can return the values ​​​​of mysql_fetch_row() and mysql_fetch_assoc() at the same time.

4. Understanding of MVC

An application completed by model, view, and controller. The model layer is responsible for providing data, and operations related to the database are handed over to the model layer for processing. The view layer provides an interactive interface and outputs data, while the controller layer is responsible for receiving requests and distributing them to the corresponding model for processing, and then calling view layer to display.

5. The principle of smarty template

smarty is a template engine. The main purpose of using smarty is to achieve the separation of logic and external content. If you do not use templates, The usual approach is to mix php code and html code. After using the template, you can put the business logic in the php file, and the template responsible for displaying the content is placed in the html file.

When Smarty executes the display method, it reads the template file, replaces the data, and generates a compiled file. After that, each access will directly access the compiled file. Reading the compiled file eliminates the need to read the template file. and string replacement time, so it can be faster. The timestamp in the compiled file records the modification time of the template file. If the template has been modified, it can be detected and then recompiled (compilation saves the static content, and the dynamic content is based on the incoming parameters vary).

If caching is enabled, a cache file will be generated based on the compiled file. During access, if there is a cache file and the cache file has not expired, the cache file will be accessed directly.

6. Implementation principle of UBB code

UBB code is a variant of HTML. We customize our tags through programs, such as "[a]UBB in PHP The essence of using tags like [/a]" is to find the [a][/a] tag and replace it with standard html. To put it bluntly, it means simplifying the standard html tag through technical means and outputting it. The result is still standard html.

After understanding the principle of ubb, it is not difficult to make a simple ubb editor. Compared with editors such as fck, the biggest advantage of ubb code is that the code is simple, has few functions, and is simple. Ubb only requires one file, and the ubb tag can be defined by yourself, which is very convenient to change. In PHP, you can use the replacement function to tag html, and convert the tag during output.

7. Please describe the purpose of the following URL rewrite rules

<IfModulemod_rewrite.c>
RewriteEngineon
RewriteCond%{REQUEST_FILENAME}!-f
RewriteCond%{REQUEST_FILENAME}!-d
RewriteBase/
RewriteRule./index.php[L]
</IfModule>

If the REQUEST_FILENAME file exists, access the file directly without performing the following rewrite rules. If the REQUEST_FILENAME directory If it exists, access the directory directly without performing the following rewrite rules. RewriteRule./index.php[L] means that all requests will be processed by index.php.

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