Conditional statement are used to perform different 
actions based on different conditions. 
If statement execute code and return True. 
If-else statement execute code and return true or false. 
else-if statement execute different codes for more 
than two conditions.

Example of If:

<?php
$day = "monday";
If($day == "Monday")
{
	echo "Have a good day!";
}
?>

Example of if-else:

<?php
$age = 30;
If($age >= 18)
{
	echo "you are young";
}
else {
	echo "you are child";
}
?>

Example of if elseif:

<?php
$per = 55;
If($per>=80)
{
	echo "A+ Grade";
}
else if($per >=70)
{
	echo "A grade";
}
else {
	echo "You are Fail";
}
?>

PHP SWITCH-case STATEMENT

Switch statement same as if statement but, there is
a difference is that switch statement is only use when
You want to compare the same variable (or expression)
with many different values and execute a different pieces
of code depending on which value it equals too. 
This is exactly the SWITCH statement.

Switch Example:

$month = 1;
switch($month) 
{
	case 1:
	echo "January";
	break;
	case 2:
	echo "Feburary";
	break;
	case 3:
	echo "March";
	break;
	.
	.
	.
	default:
	echo "Please type number between 1 to 12 ";
	break;
}