Control Structures In Php 2

Control Structures in PHP

Control Structures – if statements

if ( $a > $b )

echo "a is bigger than b";

if ( $a > $b )

{ print "a is bigger than b";

$b = $a; }

if ( $a > $b )

{ print "a is bigger than b"; }

else { print "a is NOT bigger than b"; }

if ( $a > $b )

{ print "a is bigger than b"; }

elseif ( $a == $b )

{ print "a is equal to b"; }

else { print "a is smaller than b“; }

Example usage

Example

<html>

<head><title>Your browser</title></head>

<body>

<h1>Your Browser</h1>

<p>

<?php

if( strstr($HTTP_USER_AGENT,"MSIE") )

{ echo "You are using Internet Explorer"; }

?>

to view this page.

</p>

</body>

</html>

strstr is a function which checks if its 2 nd argument is a substring of its 1 st

Control constructs -- looping

In PHP we have the following looping statements:

while - loops through a block of code if and as long as a specified condition is true

do...while - loops through a block of code once, and then repeats the loop as long as a special condition is true

for - loops through a block of code a specified number of times

foreach - loops through a block of code for each element in an array

Control constructs -- while

These are just like their counterparts in C

$i = 1;

while ( $i <= 10 )

{ echo $i++; }

$i = 0;

do { print $i; } while ( $i>0 ) ;

Control constructs -- for

These are just like their counterparts in C

for ($i = 1; $i <= 10; $i++)

{ print $i;}

Control constructs -- foreach

These are similar their counterparts in Perl

foreach(array_expression as $value)

statement

foreach(array_expression as $key => $value)

statement

<?php

$arr=array("one", "two", "three");

foreach ($arr as $value)

{echo “Number: " . $value . "<br />";}

?>

Jumping in and out of PHP mode

We can jump in and out of PHP mode even in the middle of a PHP block:

<?php

if(strstr($HTTP_USER_AGENT,"MSIE"))

{ ?> < p >You are using Internet Explorer</ p > < ?php }

else { ?> < p >You are not using Internet Explorer</ p > < ?php }

?>

Instead of using a n echo statement to print something, we jumped out of PHP mode .

N ote that the logical flow of the PHP remain s intact

Only one of the HTML blocks will be sent to the user .

A FORM and its handler in one

<html>

<head>

<title>Application Handler</title>

</head>

<body>

<?php

if (! $_POST["surname"] or !$_POST["address"]){

?>

<form method="post" action="<?php echo $_SERVER['PHP_SELF'];?>">

<p>Your surname: <input type="text" name="surname"></p>

<p>Your address: <input type="text" name="address"></p>

<input button type="submit" value= "Please send me the brochure.">

</form>

<?php

}

else{

$sn = $_REQUEST['surname'];

echo "<p>Thank you, $sn.</p>";

$addr = $_REQUEST['address'];

echo "<p> We will write to you at $addr .</p>";

}

?>

</body>

</html>

Finding out about your PHP environment

One of the many pre-defined PHP functions is phpinfo()

<html>

<body>

<h1>Your PHP Environment</h1>

<?php phpinfo(); ?>

</body>

</html>

In what follows, notice that mySQL support is enabled

Adding Comments to a PHP Script

Comments are nonprinting lines placed in code such as:

The name of the script

Your name and the date you created the program

Notes to yourself

Instructions to future programmers who might need to modify your work

Adding Comments to a PHP Script (continued)

Line comments hide a single line of code

Add // or # before the text

Choose and stick with version

Block comments hide multiple lines of code

Add /* to the first line of code

And */ after the last character in the code

Example Comments

<?php

/*

This line is part of the block comment.

This line is also part of the block comment.

*/

echo (“<h1>Comments Example</h1>”); // Line comments can follow

code statements

// This line comment takes up an entire line.

# This is another way of creating a line comment.

/* This is another way of creating

a block comment. */

?>

Control Structures In Php 2

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