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22.03.21 - PHP

Origins​

  • 1994, open source project
  • Used to be an acronym for Personal Home Page
  • Used for from handling, file processing and database access
  • Is a server-side scripting language whose scripts are embedded in HTML documents.
  • OOP language. PHP is interpreted and is dynamically typed

Basic Features​

PHP code can be specified in an HTML document using

<?php ?>

To declare and use variables use $ symbol. Dont have to specify what data type it is. Use echo to output to display, similar to how print works

Control statements are the same as C and Javascript

Strings​

converts $msgs into a string like + in java script

String functions

  • chop - remove white space from the right end
  • trim - remove white space from both ends
  • ltrim - remove white space from the left end

Arrays​

  • A PHP array is a generalisation of the arrays of other languages
  • A PHP array is a mapping of keys to values, where the keys can be numbers or strings
  • Use array() construct, which takes one or more key => value pairs as parameters and returns an array of them (basically a dictionary)
  • Loops are the same as in C and Javascript
  • Can use foreach - goes through each item in an array and does something

Array Methods​

  • is_array() - check if a variable is an array
  • unset() - to destroy an array
  • count() - to sort an array
  • shuffle() - to shuffle the elements of an array
  • explode() - to convert the words of a sentence into an array

Functions​

Objects are passed by reference Everything else by value

Other​

  • Can include library by using include
  • Can also define a class destructor - Called when you remove an object
  • Can also easily clone objects by using clone

Inheritance​

  • Data members can be declared public, private and protected
  • Can override a function implemented in the base class with a function in the derived class

To access database, use MySQLi extension. Has multiple benefits:

  • Object-oriented interface
  • Support for prepared statements
  • Support for multiple statements
  • Support for transactions

SQL​

MySQL database supports prepared statements. Used to execute the same statement repeatedly with high efficiency. Consists of 2 stages, prepare and execute.

  • Prepare stage: Statement template is sent to the database server so it can perform syntax check and initialise the server
  • Execute stage:Client binds parameter values and sends them to the server. Server then creates a statement