Conditional Statements If, If-Else, Elseif, Switch in PHP

PHP lets programmers evaluate different conditions during of a program and take decisions based on whether these conditions evaluate to true of false. Conditional statements are used to perform different actions based on different conditions.



PHP support different types of conditional statements


  • If statement
  • If-else statement
  • If-elseif-else statement
  • Switch statement

1. IF Statement – If statement is the simple condition statement. This statement Output will provide when condition must be true.

Syntax –
if (condition) {
    code to be executed if condition is true;
}

Example – Write a program to check odd number. Here number entered by user.

<!DOCTYPE html>
<html>
<head>
            <title>Check Odd</title>
</head>
<body>
<?php
            if(isset($_POST['submitbtn']))
            {
                        if($_POST['num']%2 != 0)
                        {
                                    echo "This number is Odd";
                        }
            }
?>
<form method="post">
            <input type="text" name="num" placeholder="Enter number ...">
            <input type="submit" name="submitbtn" value="Check Odd">
</form>
</body>
</html>


Example – Write a program to check number is Positive. Here number entered by user.

<!DOCTYPE html>
<html>
<head>
            <title>Check P N</title>
</head>
<body>
            <?php
                        if(isset($_POST['submitbtn']))
                        {
                                    if ($_POST['number'] > 0) {
                                                echo "Number is positive.";
                                    }
                        }
            ?>
            <form method="post">
                        <input type="text" name="number" placeholder="Enter number ...">
                        <input type="submit" name="submitbtn" value="Check No">
            </form>
</body>
</html>

2. If else statement - If-else statements allows you to display output in both the condition. If condition is true display some message otherwise display other message.

Syntax –

if(Condition)
{
     Code executed if condition is true;
}
else
{
     Code executed if condition is false;
} 

Example – Write a program to check number is positive or negative. Here number entered by user.

<!DOCTYPE html>
<html>
<head>
            <title>Check P N</title>
</head>
<body>
            <?php
                        if(isset($_POST['submitbtn']))
                        {
                                    if ($_POST['number'] > 0) {
                                                echo "Number is positive.";
                                    }
                                    else
                                    {
                                                echo "Number is negative";
                                    }
                        }
            ?>
            <form method="post">
                        <input type="text" name="number" placeholder="Enter number ...">
                        <input type="submit" name="submitbtn" value="Check No">
            </form>
</body>
</html>

3. If elseif else Statement - If you want to execute some code if one of the several conditions are true use the elseif statement. If elseif else statement executes different codes for more than two conditions.

Syntax –

If(Condition)
{
     Code executed if condition is true;
}
elseif
{
     Code executed if condition is true;
}
else
{
     Code executed if all condition is false;
}


Example – Write a program check given number is Positive, Negative or Zero.

<!DOCTYPE html>
<html>
<head>
            <title>Check P N</title>
</head>
<body>
            <?php
                        if(isset($_POST['submitbtn']))
                        {
                                    if ($_POST['number'] > 0) {
                                                echo "Number is positive.";
                                    }
                                    elseif($_POST['number'] < 0)
                                    {
                                                echo "Number is negative";
                                    }
                                    else
                                    {
                                                echo "Number is Zero";
                                    }
                        }
            ?>
            <form method="post">
                        <input type="text" name="number" placeholder="Enter number ...">
                        <input type="submit" name="submitbtn" value="Check No">
            </form>
</body>
</html>

4. Switch Statement - If you want to select one of many blocks of code to be executed, use the Switch statement. The switch statement is used to perform different actions based on different conditions.

Syntax –

switch(number)
{
     case label1:
          Code executed if number = label1;
          break;
     case label2:
          Code executed if number = label2;
          break;
     default:
     Code executed if number is different from all labels;
}

Example – Write an program print related day name according to inputted number (1-7) using switch condition.

<!DOCTYPE html>
<html>
<head>
            <title>Switch</title>
</head>
<body>
            <?php
                        if(isset($_POST['submitbtn']))
                        {
                                    if($_POST['number'])
                                    {
                                                switch ($_POST['number']) {
                                                            case '1':
                                                                        echo "Sunday";
                                                                        break;
                                                            case '2':
                                                                        echo "Monday";
                                                                        break;
                                                            case '3':
                                                                        echo "Tuesday";
                                                                        break;
                                                            case '4':
                                                                        echo "Wednesday";
                                                                        break;
                                                            case '5':
                                                                        echo "Thursday";
                                                                        break;
                                                            case '6':
                                                                        echo "Friday";
                                                                        break;
                                                            case '7':
                                                                        echo "Saturday";
                                                                        break;
                                                            default:
                                                                        echo "Wrong Choise";
                                                                        break;
                                                }
                                    }
                        }
            ?>
            <form method="post">
                        <input type="text" name="number" placeholder="Enter number ...">
                        <input type="submit" name="submitbtn" value="Check">
            </form>
</body>
</html>



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