PHP & MySQL® Web Development All-in-One Desk Reference for Dummies®

2.2. Using Conditional Statements

A conditional statement executes a block of statements only when certain conditions are true. Here are two useful types of conditional statements:

• An if statement: Sets up a condition and tests it. If the condition is true, a block of statements is executed.

• A switch statement: Sets up a list of alternative conditions. It tests for the true condition and executes the appropriate block of statements.

2.2.1. Using if statements

An if statement tests conditions, executing a block of statements when a condition is true.

2.2.1.1. Building if statements

The general format of an if conditional statement is as follows:

if ( condition )
{
   block of statements
}
elseif  ( condition )
{
   block of statements
}
else
{
   block of statements
}

The if statement consists of three parts:

• if: This part is required. Only one if is allowed. It tests a condition:

  • If the condition is true: The block of statements is executed. After the statements are executed, the script moves to the next instruction following the conditional statement; if the conditional statement contains any elseif or else sections, the script skips over them.

  • If the condition is not true: The block of statements is not executed. The script skips to the next instruction, which can be an elseif, an else, or the next instruction after the if conditional statement.

• elseif: This part is optional. You can use more than one elseif if you want. An elseif also tests a condition:

  • If the condition is true: The block ...