Why use Comments?

If you don’t work on the source code for some time, it’s easy to forget what the code does.

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Commenting the source code helps remember what the code does.

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Commenting source code is also very important when multiple developers have to lớn work on the same project. The changes made by one developer can be easily understood by other developers by simply reading the comments. As the best practice, you must have 3 lines of comments for every 10 lines of code

In this tutorial, you will learn-

PHP Comments

Comments help us to understand the code Comments are explanations that we include in our source code. These comments are for human understanding. Single line comments start with double forward slashes // and they over in the same line. Multiple line comments start with a forward slash followed by the asterisk /* & end with the asterisk followed by the forward slash */. The diagram below shows a PHP file with both multiple line và single line comments PHP Example

PHP Include và PHP Include_once

The “include” php statement is used to lớn include other files into a PHP file. It has two variations, include and include_once. Include_once is ignored by the PHP interpreter if the tệp tin to be included. The include statement has the following syntax The include_once statement has the following syntax HERE, “Include/include_once” is the statement that includes tệp tin “"file_name"” is the name of the file to be included.

Example : Include / Include_once

Suppose you are developing a website that contains the same navigation thực đơn across all the pages. You can create a common header then include it in every page using the include statement Let’s see how this can be done. We will create 2 files names header.php, index.php Below are the codes for; header.php HomeAbout usServicesContact Us index.php The header page above will output

PHP Require và PHP require_once

Example : Require

Suppose we are developing a database powered application. We can create a configuration file that we can include in all pages that connect khổng lồ the database using the require statement. Config.php Let’s now look at the sample code that requires the config file.

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Pages_model.php

Php include vs require

The difference between include / require Include Require

Issues a warning when an error occurs	Does not issue a warning
Execution of the script continues when an error occurs	Execution of the script stops when an error occurs.

Generally, it’s recommended using the include statement so that when an error occurs, execution of the script continues to display the webmaster thư điện tử address or the liên hệ us page. The require statement should be used if the entire script cannot run without the requested file. The “include” & “require” statements can be used at any line in the source codes where you want the code to lớn appear.

Summary

Single HTML code such as headers, footers, side bars etc. Can be shared across many pages. This makes it easy khổng lồ update the website by just updating a single file. PHP code such as database configuration settings, custom functions etc. Can be shared across many pages ensuring the website/application uses the same settings. Comments are used khổng lồ help understand source code. They are for human understanding Single line comment statements start with double forward slashes //. Multi-line phản hồi statements are enclosed between /* statements */. The “include, include_once, require và require_once” statements are used lớn include files. Include_once/require_once is ignored if the requested tệp tin has already been included using any of the four statements. The “include” statement issues a warning and continues with the execution if the requested tệp tin has not been found. The require statement raises a fatal error và stops the script execution. The “include” statement should be in most cases except in situations where without the requested file to be include, the entire script cannot run.