Hypertext Preprocessor (or simply PHP) is a known to be a general-purpose programming language designed for web development. PHP code may be carried out with a command line interface (CLI), fixed into HTML code, or utilized in combination with a variety of web template systems, web content management systems, and web frameworks. PHP code is more often than not processed by a PHP interpreter implemented as a web server or Common Gateway Interface (CGI) executable. The web server yields the results of the construed and executed PHP code, which might be any kind of data, such as developed HTML code or binary image data. PHP can be utilized for many programming tasks outside of the web context.
PHP is one of the popular server-side scripting languages for developing a web application.
The full form of PHP is Hypertext Preprocessor. It is used by embedding HTML for creating dynamic content, communicating with a database server, handling session etc.
There are several benefits of using PHP. First of all, it is totally free to use. So anyone can use PHP without any cost and host the site at a minimal cost.
It supports multiple databases. The most commonly used database is MySQL which is also free to use. Many PHP frameworks are used now for web development, such as CodeIgniter, CakePHP, Laravel etc.
These frameworks make the web development task much easier than before.
To be able to display the output directly to the browser, we have to use the special tags <?= and ?>.
PHP supports only single inheritance; it means that a class can be extended from only one single class using the keyword 'extended'.
'final' is introduced in PHP5. Final class means that this class cannot be extended and a final method cannot be overridden.
We use the operator '==' to test is two objects are instanced from the same class and have same attributes and equal values. We can test if two objects are referring to the same instance of the same class by the use of the identity operator '==='.
It is possible to generate HTML through PHP scripts, and it is possible to pass pieces of information from HTML to PHP.
If we would like to pass values through a form or an URL, then we need to encode and to decode them using htmlspecialchars() and urlencode().
PHP and Javascript cannot directly interact since PHP is a server side language and Javascript is a client-side language. However, we can exchange variables since PHP can generate Javascript code to be executed by the browser and it is possible to pass specific variables back to PHP via the URL.
GD library is needed to execute image functions.
imagetypes() gives the image format and types supported by the current version of GD-PHP.
The functions are getimagesize() for size, imagesx() for width and imagesy() for height.
Echo can output one or more string but print can only output one string and always returns 1.
Echo is faster than print because it does not return any value.
$message stores variable data while $$message is used to store variable of variables.
$message stores fixed data whereas the data stored in $$message may be changed dynamically.
The header() function is used to send a raw HTTP header to a client. It must be called before sending the actual output. For example, you can't print any HTML element before using this function.
Require and include both are used to include a file, but if data is not found include sends warning whereas require sends Fatal error.
The function mysqli_num_rows() returns the number of rows in a result set.
mysqli_affected_rows() return the number of entries affected by an SQL query.
The mysqli_fetch_object() function collects the first single matching record where mysqli_fetch_array() collects all matching records from the table in an array.
The PHP-OpenSSL extension provides several cryptographic operations including generation and verification of digital signatures.
When the original if was followed by: and then the code block without braces.
The session is a global variable which is used in the server to store the session data. When a new session creates the cookie with the session id is stored on the visitor's computer. The session variable can store more data than the cookie variable.
Session data are stored in a $_SESSION array and Cookie data are stored in a $_COOKIE array. Session values are removed automatically when the visitor closes the browser and cookie values are not removed automatically.
A cookie file that is stored permanently in the browser is called a persistence cookie. It is not secure and is mainly used for tracking a visitor for long times.
This type of cookie can be declared as follows,
setccookie ("cookie_name", "cookie_value", strtotime("+2 years");
$_FILE[] array contains all the information of an uploaded file.
The use of various indexes of this array is mentioned below:
$_FILES[$fieldName][‘name'] – Keeps the original file name.
$_FILES[$fieldName][‘type'] – Keeps the file type of an uploaded file.
$_FILES[$fieldName][‘size'] – Stores the file size in bytes.
$_FILES[$fieldName][‘tmp_name'] – Keeps the temporary file name which is used to store the file in the server.
$_FILES[$fieldName][‘error'] – Contains error code related to the error that appears during the upload.
It is an automated feature of PHP.
When it runs, it removes all sessions data which are not accessed for a long time. It runs on /tmp directory which is the default session directory.
Appending the session ID in every local URL of the requested page for keeping the session information is called URL rewriting.
The disadvantages of this methods are, it doesn't allow persistence between the sessions and, the user can easily copy and paste the URL and send to another user.
The full form of PDO is PHP Data Objects.
It is a lightweight PHP extension that uses consistence interface for accessing the database. Using PDO, a developer can easily switch from one database server to the other. But it does not support all the advanced features of the new MySQL server.
The average joblessness rate is likely to hoist in the job marketplace, however, the obligation of PHP developers, PHP programmers, and PHP engineers are at the upper side. Applicants with in-depth acquaintance and skill-based experience in PHP technology are expected to take the full improvement of technological expansion. Besides, PHP has occupied the highest place in the arena of programming languages as it offers a range of features to the developers. A PHP programmer is expected to take pleasure in minimum salary of 40, 000 dollars per annum. However, the salary of an experienced PHP developer can rise to double the figure mentioned before. The salaries are totally dependent upon the location, business, and the company’s requirements.
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