PHP Intro/Overview

PHP Intro/Overview

Squirrel Book pages 33-87

Server-side Scripting

Everything you need to know in one slide1.Web server (with PHP “plug-in”) gets a URL

request: http://www.site.com/page.php

2.Web server see’s that the page is .php

3.PHP Pre-processor searches the page for PHP code and executes the code.

4.Web server sends back the output of the PHP code, not the code itself.

PHP Basics

• PHP code can go anywhere in an HTML document as long as its in a PHP tag

• Example

<h1><?php echo “Hello World”; ?></h1>

PHP Variables

• Variables do NOT have strict typing • Unless math operations are used, variables are

strings by default• Variables must start with $

<?php

$x = “Hello World”;

echo $x;

?>

Commenting

• 3 Types

// Comment

# Comment

/* CommentComment */

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

• 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

• 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

$query = “ SELECT max(orderid)FROM orders

WHERE custid = $ID”;

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

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 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 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”;

Constants

define(“PI”, 3.14159);

print PI;

// outputs 3.14159

Notice that constants don’t have $Convention: Use all CAPS for constantsBTW, PHP is case sensitive

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

• Not the same as JavaScript!

$var1 = “Hello”;

$var2 = “ world”;

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

$var3 = $var1 . $var2;

Conditionals (if statements)

• Same as other high-level languages

if ($var < 5) {

print “The variable is less than 5”;

}

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: break

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

print $c . “ ”;

if ($c == 5)

break;

}

Type Conversion

$year = 2003; // This is an integer

$yearString = strval($year);

// $yearString is “2003” not an integer

Type Conversion

• string strval(any other datatype)

• integer intval(any other datatype)

• float floatval(any other datatype)

Implicit type conversion

• $var = “100” + 15;

• $var = 100 + 15.0;

• $var = 39 . “ Steps”;

• $var = 39 + “ Steps”;

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”; // error

Functions

// Function definitionfunction fname ($parameter1, $parameter2) {

code;code;…return $returnvalue;

}

// Function call$x = fname(1,2);

Variable Scope (visibility)

• Same as Java• Same as C++

function fun($x) {$temp = $x + 1;

}fun(5);print “temp is: $temp”;