if (condition1){    
//code to be executed if condition1 is true    
} elseif (condition2){      
//code to be executed if condition1 is false and condition2 is true
} elseif (condition3){      
//code to be executed if condition2 is false and condition3 is true    
....  
}  else{    
//code to be executed if all given conditions are false    
}

$x = 10;
if ($x > 0) {
	echo "$x is positive\n";
} elseif ($x < 0 ) { // if $x equals negative number
	echo "$x is negative!\n";
} else { // if $x = 0;
	echo "$x is neither positive nor negative \n";
}