In PHP, conditional statements are used to perform different actions based on different conditions.

The most commonly used conditional statements in PHP are:

1. if Statement.
2. if-else Statement
3. If-elseif-else Statement
4. Switch statement

1. if Statement : If statement is used to test a condition and execute a block of code if the condition is true.

Syntax:

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

Flowchart:

Example:

$num = 20;

if ($num > 5) 
{
   echo "The number is greater than 5.";
}

2. if-else Statement: This statement is used to check a condition and execute one block of code if the 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  
}  

Flowchart:

Example:

$num = 5;

if ($num > 10) 
{
   echo "The number is greater than 10.";
} 
else 
{
   echo "The number is less than or equal to 5.";
}

3. If-else-if-else: This statement is used to Check multiple conditions and execute different blocks of code based on those conditions.

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    
}    

Flowchart:

Example:

$num = 7;

if ($num > 10) 
{
   echo "The number is greater than 10.";
}
else if ($num > 5) 
{
   echo "The number is greater than 5 but less than or equal to 10.";
} 
else 
{
   echo "The number is less than or equal to 5.";
}

4. Switch Statement:

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

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$i = "2";switch ($i) {    case 0:        echo "i equals 0";        break;    case 1:        echo "i equals 1";        break;    case 2:        echo "i equals 2";        break;    default:       echo "i is not equal to 0, 1 or 2";}?>