Youth Tech's Online PHP Class: Lesson Four

If Statements [Chat: 8/9/02]

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Welcome back to PHP Class!  If you have any questions, as always, don't hesitate to email me.  Or, the preferred method, bring your questions to Chat, 10PM EST, every Friday!

If Statements

In any programming language, you have to be able to make decisions based on the values of variables.  In order to make these decisions, we must use if statements.  Within the if statement, we have a boolean expression to be evaluated.  ALL boolean expressions evaluate to either true or false.  You may use any of several comparison operators in these expression, the most common being:

== is equal to
!= is not equal to
<  is less than
>  is greater than
<= is less than or equal to
>= is greater than or equal to

The basic syntax of each if statement is as follows:

if(BOOLEAN_EXPRESSION){
     STATEMENTS TO BE EXECUTED IF EXPRESSION IS TRUE
}

For example:

if($A==$B){
     print "A equals B";
}

If-Else Statements

An If-Else statement allows you to specify what should be done if the boolean expression does not evaluate to true.  For example, the following should be fairly obvious as to the intentions:

if($A==$B){
     print "A equals B";
} else {
     print "A does not equal B";
}

If-Else If-Else Statements

This is simply a method for providing more  than two possible choices.

if($A==$B){
     print "A equals B";
} else if ($A>$B) {
     print "A is greater than B";
} else {
     print "A is less than B";
}

See sample source for lesson four.
See output of sample source.

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