PHP Tutorial Tutorials - PHP If Else Statements

The if construct allows for conditional execution of code fragments.
It has several statements:
The if statement
The if...else statement
The if...elseif statement
The if...elseif....else statement

if statement

if structure:

if (expr)
  statement

// statement group
if (expr){
  statement1
  statement2
}

the expr is the condition.

<?php
if ($a > $b)
  echo "a is bigger than b";
?>

<?php
  $month = 1;
  if ($month == 1) {
    echo "The month is ".$month;
    $days = 31;
  }
?>

if...else statement

the else extends an if statement to execute a statement in case the expression evaluates to FALSE.
if...else structure:

if (expr){
  // statement to be executed when expr evaluates to TRUE. 
}
else{
  // statement to be executed when expr evaluates to FALSE. 
}

<?php
$a = 5;
$b = 7;
if ($a > $b) {
  echo "a is greater than b";
} else {
  echo "a is NOT greater than b";
}
?>

if...elseif statement

elseif is a combination of if and else.
it can also be writed as else if

if...elseif structure:

if (expr1){
  // statement to be executed when expr1 evaluates to TRUE. 
} else if (expr2){
  // statement to be executed when expr1 is FALSE AND expr2 is TRUE. 
} else{
  // statement to be executed when expr1 and expr2 are both FALSE.  
}

<?php
$a = 5;
$b = 7;
if ($a > $b) {
    echo "a is bigger than b";
} elseif ($a == $b) {
    echo "a is equal to b";
} else {
    echo "a is smaller than b";
}
?>

nested if statement

If statements can be nested infinitely within other if statements.

if (expr1){
  if (expr2){
    if (expr3){
      // statement to be executed when expr1,expr2,expr3 are both TRUE. 
    }
  }
  else{
    // statement to be executed when expr1 is TRUE and expr2 is FALSE. 
  }
}
else{
  // statement to be executed when expr1 evaluates to FALSE. 
}

If statement with embedded HTML

<?php
  $a = 5;
?>

<?php if ($a == 5){ ?>
A is equal to 5
<?php } ?> 

Alternative syntax for If statement

In If statement, We can change the opening brace to a colon: and the closing brace to endif;;
For example:

<?php
    $a = 3;
    if ($a == 1):
        echo "a = 1";
    elseif ($a == 2):
        echo "a = 2";
    else:
        echo "a is neither 1 nor 2 ";
    endif;
?>