Web Application Development using PHP Chapter 2

CN5109
WEB APPLICATION
DEVELOPMENT
Chapter 2
PHP – Conditional and Loop Statements

Conditional Statements
• Conditional statements are used to perform different actions
based on different conditions.
• It perform different computations or actions depending on
whether a programmer-specified boolean condition evaluates
to true or false.

Conditional Statements
• The following are conditional statements in PHP:
• if statement - executes some code if one condition is
true
• if...else statement - executes some code if a condition
is true and another code if that condition is false
• if...elseif....else statement - executes different codes
for more than two conditions
• switch statement - selects one of many blocks of code
to be executed

IF Statement
• The if statement executes some code if one condition is true.
Syntax:
if (condition) {
code to be executed if condition is true;
}

IF Statement
• Example:
<?php
$t = 15;
if ($t < 20) {
echo "Have a good day!";
}
?>
Output:

IF … ELSE Statement
• The if....else statement executes some code if a condition is
true and another code if that condition is false.
Syntax:
if (condition) {
code to be executed if condition is true;
}
else {
code to be executed if condition is false;
}

IF … ELSE Statement
• Example:
<?php
$t = 15;
if ($t < 20) {
}
else {
echo "Have a good night!";
}
?>
Output:

IF … ELSEIF … ELSE Statement
• The if....elseif...else statement executes different codes for
more than two conditions.
Syntax:
if (condition) {
code to be executed if this condition is true;
} elseif (condition) {
code to be executed if this condition is true;
} else {
code to be executed if all conditions are false;
}

IF … ELSEIF … ELSE Statement
• Example:
<?php
$t = 5;
if ($t < 10) {
echo "Have a good morning!";
} elseif ($t < 20) {
} else {
echo "Have a good night!";
}
?>
Output:

SWITCH Statement
• The switch statement is used to perform different actions
based on different conditions.
Syntax:
switch (n) {
case label1:
code to be executed if n=label1;
break;
case label2:
break;
case label3:
break;
...
default:
code to be executed if n is different from all labels;
}

SWITCH Statement
• Example:
<?php
$favcolor = "red";
switch ($favcolor) {
case "red":
echo "Your favorite color is red!";
break;
case "blue":
echo "Your favorite color is blue!";
break;
case "green":
echo "Your favorite color is green!";
break;
default:
echo "Your favorite color is neither red, blue, nor green!";
}
?>
Output:

Quiz
a. What do CONDITIONAL STATEMENTS used for?
b. List down any four examples of CONDITIONAL STATEMENTS.

Quiz
Write a PHP code using Conditional Statement:
If AGE below 18, display message “You cannot enter.”
If MARKS more than 39, display message “You Passed!”
Else, display message “You Failed!”
Write one example using SWITCH Statement

Loop Statements
• A loop statement in programming performs predefined tasks
while or until a predetermined condition is met.
• The following looping statements in PHP:
• while - loops through a block of code as long as the
specified condition is true
• do...while - loops through a block of code once, and
then repeats the loop as long as the specified
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

WHILE Loop
• The while loop executes a block of code as long as the
specified condition is true.
Syntax:
while (condition is true) {
code to be executed;
}

WHILE Loop
Example:
<?php
$x = 1;
while($x <= 5) {
echo "The number is: $x <br>";
$x++;
}
?>
Output:

DO … WHILE Loop
• The do...while loop will always execute the block of code once,
it will then check the condition, and repeat the loop while the
specified condition is true.
Syntax:
do {
} while (condition is true);

DO … WHILE Loop
Example:
<?php
$x = 1;
do {
$x++;
} while ($x <= 5);
?>
Output:

FOR Loop
• The for loop is used when you know in advance how many
times the script should run.
• Parameters:
• init counter: Initialize the loop counter value
• test counter: Evaluated for each loop iteration. If it evaluates to
TRUE, the loop continues. If it evaluates to FALSE, the loop ends.
• increment counter: Increases the loop counter value
Syntax:
for (init counter; test counter; increment counter) {
} condition is true);

FOR Loop
Example:
<?php
for ($x = 20; $x <= 15; $x++) {
}
Echo “End loop”;
?>
Output:

FOREACH Loop
• The foreach loop works only on arrays, and is used to loop
through each key/value pair in an array.
Syntax:
foreach ($array as $value) {
}

FOREACH Loop
Example:
<?php
$numbers = array(1,45,3,90);
foreach ($numbers as $value) {
echo "$value <br>";
}
?>
Output:

Quiz
a. Define LOOP STATEMENT.
b. Explain the difference between WHILE Statement and DO …
WHILE Statement.
c. Write a PHP code using FOR Loop Statement to display
number 10 to 30.

Web Application Development using PHP Chapter 2

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Web Application Development using PHP Chapter 2