just a little php programming php on the server. common programming language features comments data...
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Just a Little PHP
Programming PHP on the Server
Common Programming Language Features
• Comments• Data Types• Variable Declarations• Expressions• Flow of Control Statements• Functions and Subroutines• Macros and Preprocessor Commands• I/O Statements• Libraries• External Tools (Compiler, debugger etc)
PHP like JavaScript is Embedded in Web Pages
The difference is that a PHP file is executed by the Server BEFORE being sent to the client. Just like CGI.
<html> <body> <!- - Regular HTML -- > <?php
//Your PHP goes here ?> <!- - More HTML - -></html>
Comments
// This is a single line comment
/* This is a multiline comment just like C */
# works as a comment, just like the bash shell
Data Types
PHP is a weakly typed language.
Any variable can be any data type
The available data types are:
•boolean•number (integer and float)•string•array•object
Variable Names
To declare a scalar variable just use it.
Variable names begin with a $, ie:
$x=7;echo $counter;
#Assignment - all variables preceded by $ #whether on the left or the right$x=$myValue*2
Using Quotes
$x=‘The contents $var of this string are literally’;$y=“But $var is the value of the variable”;$z=`uptime`; #Run as a shell command, stored in $z$a=“Quoting in \$doubleQuotes \n<br>”;k
Constants
Numeric: 4.2 17.5 1.6E+7 21 0x2A
String: “Hello” ‘Nice Day’ Bob
define(“MYCONSTANT”, 42);
echo MYCONSTANT
If a constant is not defined it stands for itself, ie: Bob. Otherwise it stands for its value. Constants should be ALLCAPS and do not use a $ before the name
Creating an Array
$list[0] = 17; //This creates an array
$list = array(1,2,3 4,5); //creates an indexed array
$list = array(“Smith” => “Carpenter, “Jones”=> “Technician”, “Rajiv” => “Manager”); //Associative array
$n=sizeof($list);
OperatorsArithmetic: Regular C style operators
= + - * / % += -= *= /= ++ --
Relational: == != <> > < >= <= Note: “4” == 4 is True
String: “a” . $b $a.=$b;
Logical: && || !
Web Page Output
echo “The size of my array is: “ . $n;
print “Hello World: “ . $n;
printf “There are %4d items in my array, %s\n”, $n, $name;
printf uses the same format codes that C uses: %d (integer) %f (float) %x (hex) %s (string)
(There is one new format code: %b - binary)
Dumping an Array
print_r($anyArry);
#The entire array is dumped to the screen
if/then/else
if ($price <10 || $price>20){ printf “%10.2f is a reasonable price<br>”, $price; $total+=$price; }else echo “Try again!”;
switch
switch($choice){ case 1: case ‘beer’: doSomething(); ... break; case ‘prezels: doSomethingElse(); ... break; default: echo “Unknown option”;}
Simple for loops
for($i=1;$i<10;$i++){ $sum+=$i; echo “Running total is: “ + $sum + “<br>”; }
echo “Final total is: “ $sum;
Looping Through Associative Arrays
foreach( $array as $key => $value){ echo “Key: “ . $key echo “Value: “ . $value; }
Note: Associative Arrays and Indexed Arrays are the same thing. The key values for an indexed array are: 0, 1, 2 .....
Functions in PHP
function myFunction($arg1, $arg2, $arg3){ //Do some calculation ie:
$result= ($arg1 + $arg2) % $arg3;
return $result; }
Including a library of functions
include (“myLibraryFile.php”);
require(“myLibrary.php”);
require_once(“myLibrary.php”);
Use any of:
Debugging Php
In the same directory as your php program, include the file php.ini:
display_errors=on
A missing quote may result in a blank web page. Test your program for syntax error on the command line where it will show up:
$bash 3.2: php yourProg.php
Debugging ContinuedIn every PHP program include the following as thevery first commands:<?php ini_set(‘display_errors’,1); error_reporting(E_ALL); ...
?>
Strategies:•Always comment your code FIRST•Comment out blocks of code to isolate the error•Narrow down syntax errors to a single line.•Split complex lines into smaller stages•Use echo and printf statements liberally
Important PHP Variables Purpose$_GET, $_POST, $_COOKIE$_REQUEST
Data sent between client and server.$_REQUEST includes all 3
$REMOTE_ADDR IP of the client$HTTP_REFERER Previous Web Page $REQUEST_TIME When page was requested
(EPOCH time)
$HTTP_USER_AGENT Browser Info
$_SERVER Array of Server related values
SQL FunctionsMYSQL FUNCTION CALL EXPLANATION
mysql_error() Report on last error
mysql_connect(host,user, pass) connects to database; returns a connection to the database
mysql_selectdb(dbName) use specified schema
$result=mysql_query(stmt) runs stmt against the databasereturns 0 to n rows for SELECTreturns number of rows affected for INSERT, UPDATE or DELETE
$row=mysql_fetch_array($result)
creates an associative array using column names as keys
mysql_close($con) closes the database connection
SQL FunctionsSome PHP Functions EXPLANATION
date(‘r’) The current date as a string
time() current time
die(message) print out a message and quit
include(‘fileName’)require_once(‘fileName’);
include an external PHP file – allows shared code and libraries
header(‘attribute: value’) adds a header to the response
PHP Has A Rich Set of Library Functions
THE END