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) { echo "Have a good day!"; } 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) { echo "Have a good day!"; } 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: code to be executed if n=label2; break; case label3: code to be executed if n=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 { code to be executed; } while (condition is true);

DO … WHILE Loop Example: <?php $x = 1; do { echo "The number is: $x <br>"; $x++; } while ($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) { code to be executed; } condition is true);

FOR Loop Example: <?php for ($x = 20; $x <= 15; $x++) { echo "The number is: $x <br>"; } 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) { code to be executed; }

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