03loop conditional statements

Loops and

Conditional Statements

Definition of Loop

In computer programming, a loop is a sequence of instruction(s) that is continually repeated until a certain condition is reached

OR

Loops execute a block of code while the specified condition is true.

Topic: Loops & Conditional Statements

Loop Types

for - loops through a block of code a specified number of times 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 foreach - loops through a block of code for each element in an

array


Basic Operations for Loop Initialization: - this step is a first execute in for

loop .initialization step is allows declaration of variable. This step is starting point of for loop statement in php.

Condition: - second step of for loop is condition, if condition is true then body part is execute .otherwise body part is not execute in php.

increment/decrements: - this step through declare variable increment and decrements in php(it means declare variable update to the increment and decrements).

Statements: - this part is body part. All three step are execute then body part is executed .in this part display any type of message in web page.


For loop The for statement is used when you know how many times you

want to execute a statement or a block of statements.

Syntax for ( initialization; condition; increment/decrements )

{ statement(s);

}


For loop (Example)Example

$a = 0;$b = 0;for( $i=0; $i<5; $i++ ){ $a += 10; $b += 5; echo $a. “ "; echo $b.“ ";}echo ("At the end of the loop a=$a and b=$b" );

Output10 5 20103015 40205025 At the end of the loop a=50 and b=25

While loop

The while looping statement will execute a block of code if and as long as a test expression is a true.

SYNTAX while(condition)

{ statement(s);

increment/decrements; }


While loop (Example)Example

$i = 0; $num = 50; while( $i < 10)

{ echo $i.“ "; echo $num." "; $num--;

$i++; }

echo ("Loop stopped at i = $i and num = $num" );

0501492483474465

45644743842941Loop stopped at i = 10 and num = 40

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

{ statement(s); increment/decrements; } while( condition );


Do while loop (Example)Example

$i = 0; do{ echo $i.“ ";

$i++; }while( $i < 10 ); echo ("Loop stopped at i = $i" );

0123456789Loop stopped at i = 10

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)

{ Statement;

}


foreach loop (Example)Example

$array = array( 1, 2, 3, 4, 5);foreach( $array as $value )

{ echo "Value is $value.“ ”;

}

Value is 1Value is 2Value is 3Value is 4Value is 5

Output

Decision Making | Conditional Statements

The if, else if ...else and switch statements are used to take decision based on the different condition. You can use conditional statements in your code to make your decisions. PHP supports following three

decision making statements: if...else statement - use this statement if you want to execute a

set of code when a condition is true and another if the condition is not true

else if statement - is used with the if...else statement to execute a set of code if one of several condition are true

switch statement - is used if you want to select one of many blocks of code to be executed, use the Switch statement. The switch statement is used to avoid long blocks of if..else if..else code.


The if Statement The if statement is used to execute some code only if a specified condition is

trueSYNTAX

if (condition) { code to be executed if condition is true;

}

Example<?php $t = date("H");if ($t < "20") {

echo "Have a good day!"; } ?>

The if...else Statement Use the if....else statement to execute some code if a condition is true and another code if the

condition is false.SYNTAX

if (condition) { code to be executed if condition is true; } else {

code to be executed if condition is false; }

Example<?php $t = date("H");if ($t < "20") {

echo "Have a good day!"; } } else {

echo "Have a good night!"; }?> Topic: Loops & Conditional Statements

The if...else if....else Statement Use the if....elseif...else statement to specify a new condition to test, if the first

condition is false. SYNTAX

if (condition) { code to be executed if condition is true;

} else if (condition) { code to be executed if condition is true;

} else { code to be executed if condition is false;

}


The if...else if....else Statement(Example)

Example$t = date("H");if ($t < "10") {

echo "Have a good morning!"; } else if ($t < "20") {

echo "Have a good day!"; } else {

echo "Have a good night!"; }

Switch Statement Use the switch statement to select one of many blocks of code to be executed.

SYNTAXswitch (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; } Topic: Loops & Conditional Statements

Switch StatementEXAMPLES

$favcolor = "red"; switch ($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!";

} Topic: Loops & Conditional Statements

Difference Between if & switch

IF Statement: Checks the value of data is less than or greater than. (In ranges). Example:

can tell whether an input age is more than 18 and less than 60.

Switch Case: Checks the value of data that is pre-specified. Only equal to.

Example: Can only generate output if the value matches. When the age is 18 or

when the age is 60. No comparison of data based on greater than or smaller than. Compares data based on equality


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03loop conditional statements

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