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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
Topic: Loops & Conditional Statements
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.
Topic: Loops & Conditional Statements
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);
}
Topic: Loops & Conditional Statements
For loop (Example)Example
$a = 0;$b = 0;for( $i=0; $i<5; $i++ ){ $a += 10; $b += 5; echo $a. “<br>"; echo $b.“<br>";}echo ("At the end of the loop a=$a and b=$b" );
Output10 5 20103015 40205025 At the end of the loop a=50 and b=25
Topic: Loops & Conditional Statements
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; }
Topic: Loops & Conditional Statements
While loop (Example)Example
$i = 0; $num = 50; while( $i < 10)
{ echo $i.“<br>"; echo $num."<br>"; $num--;
$i++; }
echo ("Loop stopped at i = $i and num = $num" );
0501492483474465
45644743842941Loop stopped at i = 10 and num = 40
Output
Topic: Loops & Conditional Statements
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 );
Topic: Loops & Conditional Statements
Do while loop (Example)Example
$i = 0; do{ echo $i.“<br>";
$i++; }while( $i < 10 ); echo ("Loop stopped at i = $i" );
0123456789Loop stopped at i = 10
Output
Topic: Loops & Conditional Statements
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;
}
Topic: Loops & Conditional Statements
foreach loop (Example)Example
$array = array( 1, 2, 3, 4, 5);foreach( $array as $value )
{ echo "Value is $value.“<br>”;
}
Value is 1Value is 2Value is 3Value is 4Value is 5
Output
Topic: Loops & Conditional Statements
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.
Topic: Loops & Conditional Statements
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!"; } ?>
Topic: Loops & Conditional Statements
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;
}
Topic: Loops & Conditional Statements
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!"; }
Topic: Loops & Conditional Statements
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
Topic: Loops & Conditional Statements
THANKYOU
Topic: Loops & Conditional Statements