If Statement in PHP

If statement is a conditional statement that decides the flow of statements. If is one of the important statements in programming languages.
The syntax of PHP if conditional statement is just like any other programming langauge.

Syntax :

if (expression) {
  statements  or block or statements
  }

The expression is evaluated by the if statement return a boolean value (i.e. either true or false).

If the boolean value returned is true the block of statements with if are executed else not.

If we have two variable $x and $y to be evaluated in if condition then, if($x == $y) : returns true if x is equal to y if($x != $y)  : returns true if x is not equal to y if($x < $y)   : returns true if x is less than y if($x > $y)   : returns true if x is greater than y if($x <= $y) : returns true if x is less than or equal to y if($x >= $y) : returns true if x is greater than or equal to y

Example :

<?php

$a = 20;
$b = 20;
$c = 20;

if($a == $b)  // a is equal to b , hence returns boolean true
{
	echo "Value of a = ".$a."<br>";
	echo "Value of b = ".$b."<br>";
	echo "a is equal to b";
}

if($a == $c)  // a is not equal to b , hence returns boolean false
{
	echo "Value of a = ".$a."<br>";
	echo "Value of c = ".$c."<br>";
	echo "a is equal to c";
}

?>

Output
	

Value of a = 20
Value of b = 20
a is equal to b

In the above example value of a and b is equal hence first if condition returns TRUE, so the if block is being executed. Where as a and c are not equal thus if block two is not executed.

If-else Statements

As we see the if block is executed only when the expression/condition is held true, but some times we would like to execute certain statements if the condition is not met, so for this we have the if-else statements.
Syntax :

if (expression) {
  statement or block or statements
  }
else {
  statements or block or statements
}

<?php

$a = 20;
$b = 20;
$c = 20;



/* a is equal to b,  
hence returns boolean true and "if" block is executed */ 

if($a == $b)
{
	echo "Value of a = ".$a."<br>";
	echo "Value of b = ".$b."<br>";
	echo "a is equal to b<br><br>";
}
else {
	echo "Value of a = ".$a."<br>";
	echo "Value of b = ".$b."<br>";
	echo "a is not equal to b<br><br>";
}


/* a is not equal to b , hence returns 
boolean false and "else" block is executed */ 

if($a == $c)  
{
	echo "Value of a = ".$a."<br>";
	echo "Value of c = ".$c."<br>";
	echo "a is equal to c";
}
else {
	echo "Value of a = ".$a."<br>";
	echo "Value of c = ".$c."<br>";
	echo "a is not equal to c<br>";
	
}

?>

Output
	

Value of a = 20
Value of b = 20
a is equal to b

Value of a = 20
Value of c = 20
a is equal to c

The if-else statement just improvises the if statement example. If a statement returns boolean false then now the else block is being executed.

If we have only one statement in if or else condition statements, we do not require braces e.g. if(2 > 5)    echo "2 > 5 : true"; else    echo "2 > 5 : false";

If elseif else Statements

We may have a case where in we have multiple if statements and only one of with holds true. In such case we use If elseif else statements
Example to check the day of week.

<?php

$day=5;

if($day == 1)
	echo "Its a Monday!";

elseif ($day == 2)
	echo "Its a Tuesday!";

elseif ($day == 3)
	echo "Its a Wednesday!";

elseif ($day == 4)
	echo "Its a Thursday!";

elseif ($day == 5)
	echo "Its a Friday!";

elseif ($day == 6)
	echo "Its a Saturday!";

else {
	echo "Its a Sunday!!<br>";
	echo "Its a Holiday!!<br>";
}

?>

Output
	

Its a Friday!