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PHP Intro/Overview. Bird Book pages 1-11, 39-106. Server-side Scripting. Everything you need to know in one slide Web server (with PHP “plug-in”) gets a URL http://www.site.com/page.php Web server see’s that the page is . php

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php intro overview

PHP Intro/Overview

Bird Book pages 1-11, 39-106

server side scripting
Server-side Scripting

Everything you need to know in one slide

  • Web server (with PHP “plug-in”) gets a URLhttp://www.site.com/page.php
  • Web server see’s that the page is .php
  • PHP Pre-processor searches the page for PHP code and executes the code.
  • Web server sends back the output of the PHP code, not the code itself.
php basics
PHP Basics
  • PHP code can go anywhere in an HTML document as long as its in a PHP tag
  • Example

php variables
PHP Variables
  • Variables do NOT have strict typing
  • Unless math operations are used, variables are strings by default
  • Variables must start with $

$x = “Hello World”;

echo $x;

?>

commenting
Commenting
  • 3 Types

// Comment

# Comment

/* Comment

Comment */

print and echo
Print and Echo
  • Print can print strings

print “42”;

  • Echo is more robust than print, it can print numbers and more than one parameter, separated by commas

echo 42; // This will actually print 42

$x = “is”

echo “The answer ”, $x, “ ”, 42;

single quotes vs double
Single Quotes vs. Double
  • These are the same…

print “This works.”;

print ‘This works also.’;

  • This makes it easy to print quotes

print “Here is a ‘single quote’ ”;

print ‘Here is a “double quote” ’;

new lines
New lines
  • The string variable $var contains a new line character  “Hello there\n sir!”

$var = “Hello there

sir!”;

  • Introducing new lines breaks makes it easer to write SQL queries that work…
sql example
SQL Example

$query = “ SELECT max(orderid) FROM orders

WHERE custid = $ID”;

  • If you send this query string to some database server it is important that the new line characters are in the string.
variables in strings
Variables in strings

$x = 256

// “My computer has 256 MB ram.”

$message = “My computer has $x MB ram.”;

// “My computer has.”

$message = “My computer has $xMB ram.”;

Why?

variables in strings1
Variables in strings

$x = 256

// “My computer has.”

$message = “My computer has $xMB ram.”;

// “My computer has 256MB ram.”

$message = “My computer has {$x}MB ram.”;

variables in strings2
Variables in strings

Using { } is very important when trying to include complex variables into other strings.

$message = “Mars has a diameter of {$planets[‘Mars’][‘dia’]}.”;

variables
Integers

$var1 = 10;

Floats

$var2 = 6.1;

Boolean

$var3 = true;

String

$var4 = “true”;

$var5 = ‘true’;

$var6 = ‘10’;

$var7 = “6.1”;

Variables
constants
Constants

define(“PI”, 3.14159);

print PI;

// outputs 3.14159

Notice that constants don’t have $

Convention: Use all CAPS for constants

BTW, PHP is case sensitive

expression and operators
Expression and Operators
  • Same as most high-level languages

$z = 3;

$x = 1;

$y = 5.3;

$z = $x + $y;

$z++;

$x += $y + 10;

$z = $x * 10;

string concatenation
String concatenation
  • Not the same as JavaScript!

$var1 = “Hello”;

$var2 = “ world”;

$var3 = $var1 + $var2; //This won’t work

$var3 = $var1 . $var2;

conditionals if statements
Conditionals (if statements)
  • Same as other high-level languages

if ($var < 5) {

print “The variable is less than 5”;

}

compound conditionals
Compound conditionals

if ($x == 1) {

print “x is 1”;

}

elseif ($x == 2) { //  Notice elseif is one word

print “x is 2”;

}

else {

print “x is not 1 and not 2”;

}

loops
While

$c = 0;

while ($c < 10) {

print $c . “ ”;

$c++;

}

For

for ($c = 0; $c < 10; $c++) {

print $c . “ ”;

}

Loops
loops break
Loops: break

for ($c = 0; $c < 10; $c++) {

print $c . “ ”;

if ($c == 5)

break;

}

type conversion
Type Conversion

$year = 2003; // This is an integer

$yearString = strval($year);

// $yearString is “2003” not an integer

type conversion1
Type Conversion
  • string strval(any other datatype)
  • integer intval(any other datatype)
  • float floatval(any other datatype)
implicit type conversion
Implicit type conversion
  • $var = “100” + 15;
  • $var = 100 + 15.0;
  • $var = 39 . “ Steps”;
  • $var = 39 + “ Steps”;
implicit type conversion1
Implicit type conversion
  • $var = “100” + 15; // $var becomes int
  • $var = 100 + 15.0; // $var becomes float
  • $var = 39 . “ Steps”; // $var becomes string
  • $var = 39 + “ Steps”; // $var become int
functions
Functions

// Function definition

function fname ($parameter1, $parameter2) {

code;

code;

return $returnvalue;

}

// Function call

$x = fname(1,2);

variable scope visibility
Variable Scope (visibility)
  • Same as Java
  • Same as C++

function fun($x) {

$temp = $x + 1;

}

fun(5);

print “temp is: $temp”;

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