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if-else Statement

Explore how to implement the if-else statement in PHP to manage decision-making in your code. Understand the syntax, best practices like using braces, and how to handle nested if statements for complex conditions. This lesson helps you write clearer conditional logic for your PHP programs.

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Conditionals in PHP

Programs often need to make decisions based on different inputs or conditions. In PHP, these decisions are handled using conditionals. One of the simplest and most useful conditionals in PHP is the if-else statement.

if and else in PHP

Let’s start by taking a look at an example which checks if a variable a is greater than or less than b. In this example, assume that a and b are not equal, so one of the two branches will always execute:

PHP
<?php
$a = 50; //change the value of "a" so its less than b in order to execute the else statement
$b = 15;
if ($a > $b)
{
    //this code is executed only if $a is greater than $b
    echo "a is greater than b";
}
else
{
    //this code is executed if the preceding "if" condition evaluated to false
    echo "a is less than b";
}
?>

The figure below illustrates how the working of the above code snippet using a flow chart:

Explanation

Line 4:

  • In this line note that there is space between the keyword if and the opening parenthesis.

  • Inside the parentheses is the condition; in this case, it is a comparison using greater than operator between two values.

  • It is a good practice to use the same type of arguments (not comparing floating-point values to characters).

  • Note also the left curly brace {. This symbol denotes a block of multiple lines of code. Without it, the conditional would only refer to the statement immediately following it.

  • It is a good practice to always use the braces.

Line 6:

  • This comment represents the body of the conditional statement.

Line 8:

  • The right curly brace is essential; it matches the opening brace on line 4 and signals the end of the if body.

  • This line is optional. If there is a sort of “default” behavior that should be carried out, it would be placed here.

  • The else clause does not belong by itself, only directly following an if clause.

Line 10:

  • This is the body of the else clause.

Line 11:

  • This curly brace is also essential; it matches the opening brace on line 8 and signals the end of the else body.

The body of the else block can be another if statement. This is known as “nested conditionals” because the conditionals are indeed nested; that is, placed inside of one another.

Nested-If

Here one if-else block is nested within another. One has to be careful in closing the inner if before closing the outer if.

C++
if(condition1){
  //execution statement(s) 
  if(condition2){
    //execution statement(s)
  }//end of inner if
  else{
    //execution statement(s)
 }//end  of inner else
}//end ofouter if
else{
  //execution statement(s) 
}//end ofouter else

Explanation

In the code block above if

  • condition1 is true then

    • after executing the execution statement(s), code flows to the condition2 check.

    • Based on the result either execution statement(s) of the nested if or else are executed.

  • condition1 is false then

    • code flows to else statement in line 13 and the execution statements of this else get executed.

Now let’s take a look at the if-elseif-else statement, another common way to write conditionals in PHP.