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PHP Intro/Overview

PHP Basics

• PHP code can go anywhere in an HTML

document as long as its in a PHP tag

• Example

Commenting

• 3 Types

// Comment

# Comment

/* Comment

Comment */

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;

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 server it is important that the

new line characters are in the string.

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’]}.”;

Constants

define(“PI”, 3.14159);

print PI;

// outputs 3.

Notice that constants don’t have $

Convention: Use all CAPS for constants

BTW, 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;

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: 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