Wednesday 13 March 2013

PHP Introduction

PHP

  • PHP stands for: Hypertext Preprocessor.
  • PHP is a server-side scripting language.
  • PHP scripts are executed on the server.
  • PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.).
  • PHP files can contain text, HTML tags and scripts.
  • PHP files are returned to the browser as plain HTML
  • A PHP scripting block always starts with <?php and ends with ?>
Below, we have an example of a simple PHP script which sends the
text "Hello World" to the browser:

<?php echo "Hello!word"; ?>
  • Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.
  • There are two basic statements to output text with PHP: echo and print. In the example above we have used the echo statement to output the text "Hello World".
  • Note: The file must have a .php extension. If the file has a .html extension, the PHP code will not be executed. 
  • In PHP, we use // to make a single-line comment or /* and */ to make a large comment block.
<html>
<body>

<?php
//This is a comment

/*
This is
a comment
block
*/
?>
</body>
</html>

Variables in PHP

Variables are used for storing values, like text strings, numbers or arrays.
When a variable is declared, it can be used over and over again in your
script. All variables in PHP start with a $ sign symbol.
The correct way of declaring a variable in PHP:


$var_name = value;

<?php
$txt="Hello World!";
$x=16;
?>


In PHP, a variable does not need to be declared before adding a value to
it Below, the PHP script assigns the text "Hello World" to a string variable
called $txt:

<?php
$txt="Hello World";
echo $txt;
?>

The output of the code above will be:
Hello World

The Concatenation Operator


There is only one string operator in PHP. The concatenation operator (.) is used to put two string values together.
To concatenate two string variables together, use the concatenation
operator:

<?php
$txt1="Hello World!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>

 The output of the code above will be:

Hello World! What a nice day!

If we look at the code above you see that we used the concatenation
operator two times. This is because we had to insert a third string (a
space character), to separate the two strings.


The strlen() function


The strlen() function is used to return the length of a string.
Let's find the length of a string:

<?php
echo strlen("Hello world!");
?>

The output of the code above will be:
12

The length of a string is often used in loops or other functions, when it is
important to know when the string ends. (i.e. in a loop, we would want to
stop the loop after the last character in the string). 

No comments:

Post a Comment