PHP Basics

PHP Basics#

Starting out#

PHP files are run on the server. In Apache the are usually placed in a folder within the HTDOCS folder.

PHP code is placed between the

 <?php

   ....

  ?>

This can be placed anywhere - in the head or body and multiple times

Syntax#

  • Statements end with ;

  • PHP statements, key words, classes etc are NOT case sensitive

  • Variables are case sensitive

Comments#

//  single line
# single line
    
/* multiple line
Comments
*/

Variables#

  • Start with $

  • Followed by a letter or underscore

  • Cannot start with a number

  • Variables are case sensitive

  • No special characters except for underscore _

  • Variables are created when a value is assigned to it

  • VARIABLES ARE LOOSELY TYPE

    • They can hold anything

    $salary = 20000;
$_salary = 1000000;

Constant#

//Note constants do not use $ and the convention is to use all caps
//use the define command

        define('PI', 3.1415);
        define('CODEGURU', "Jim Goudy");

Variable Scope - Local#

<?php
 // The variable can only be accessed within the function   
    
function myfunc()
{
	$x=42; 			//local scope
	echo (“This is value x is $x”);	//note that the variable is within the string
}

myfunc();
?>

Variable Scope - Global#

<?php
// The variable can only be accessed from outside the function

//global scope
$x=42; 				

function myfunc()
{
    //note that the variable is within the string
	echo “This is value x is $x”;	
}

myfunc();
?>

Global is also a keyword - supervariable

Variable Scope - Static#

The variable will retain its value after it’s been called by a function.

Usually when a function is called the variables are cleared and reinitialized

<?php

function myfunc2()

{

 static $xx=42;  //local scope

 echo “This is value x is $x”; //note that the variable is within the string

$xx = $xx + 100;

echo("<br>This is value x is $xx<br><hr><br>");

}

myfunc2();

myfunc2();

?>
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