Conditional Statement in PHP

Flow control statements in PHP are used to determine the order in which a program's instructions are executed. They allow you to create decision-making structures, loops, exception handling, and more.

In PHP we have the following conditional statements:

• if statement - executes some code if one condition is true.
• if...else statement - executes some code if a condition is true and another code if that condition is false.
• if...elseif...else statement - executes different codes for more than two conditions.
• switch statement - selects one of many blocks of code to be executed.

1. if Statement

PHP if statement allows conditional execution of code. It is executed if condition is true.

If statement is used to executes the block of code exist inside the if statement only if the specified condition is true.

Syntax

if(condition){
	//code to be executed
}
 

Example

<?php
	$num=12;
		if($num<100){
		echo "$num is less than 100";
	}
?>

2. If-else Statement

PHP if-else statement is executed whether condition is true or false.

If-else statement is slightly different from if statement. It executes one block of code if the specified condition is true and another block of code if the condition is false.

Syntax

if(condition){ 
	//code to be executed if true 
}else{ 
	//code to be executed if false 
}

Example

<?php
	$num=12;
	if($num%2==0){
		echo "$num is even number";
	}else{
		echo "$num is odd number";
	}
?>

3. If-else-if Statement

The PHP if-else-if is a special statement used to combine multiple if?.else statements. So, we can check multiple conditions using this statement.

Syntax

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

Example

<?php
	$marks=69;
	if ($marks<33){
		echo "fail";
	}
	else if ($marks>=34 && $marks<50) {
		echo "D grade";
	}
	else if ($marks>=50 && $marks<65) {
		echo "C grade";
	}
	else if ($marks>=65 && $marks<80) {
		echo "B grade";
	}
	else if ($marks>=80 && $marks<90) {
		echo "A grade";
	}
	else if ($marks>=90 && $marks<100) {
		echo "A+ grade";
	}
	else {
		echo "Invalid input";
	}
?>

4. nested if Statement

The nested if statement contains the if block inside another if block. The inner if statement executes only when specified condition in outer if statement is true.

Syntax

if (condition) {
	//code to be executed if condition is true
	if (condition) {
		//code to be executed if condition is true
	}
}

Example

<?php
	$age = 23;
	$nationality = "Nepali";
	//applying conditions on nationality and age
	if ($nationality == "Nepali")
	{
		if ($age >= 18) {
			echo "Eligible to give vote";
		}
		else {
			echo "Not eligible to give vote";
		}
	}
?>

5. Switch Case

PHP switch statement is used to execute one statement from multiple conditions. It works like PHP if-else-if statement.

Important points to be noticed about switch case:

• The default is an optional statement. Even it is not important, that default must always be the last statement.
• There can be only one default in a switch statement. More than one default may lead to a Fatal error.
• Each case can have a break statement, which is used to terminate the sequence of statement.
• The break statement is optional to use in switch. If break is not used, all the statements will execute after finding matched case value.
• PHP allows you to use number, character, string, as well as functions in switch expression.
• Nesting of switch statements is allowed, but it makes the program more complex and less readable.
• You can use semicolon (;) instead of colon (:). It will not generate any error.

Syntax

switch(expression){
	case value1:
		//code to be executed
	break;
	case value2:
		//code to be executed
	break;
	......
	default:
		code to be executed if all cases are not matched;
}

Example

<?php
	$num=20;
	switch($num){
		case 10:
			echo("number is equals to 10");
		break;
		case 20:
			echo("number is equal to 20");
		break;
		case 30:
			echo("number is equal to 30");
		break;
		default:
			echo("number is not equal to 10, 20 or 30");
	}
?>