==== If ElseIf Else ====

The **''If''** code block allows you to selectively execute program code based on when a condition is met.  For instance, you may want to output a message based on the score for a student in the class.  An example of this is shown below...

<code php>
// one-line if statement
if ($score >= 60) echo 'You Pass!';

// if statement in a code block
if ($score >= 90) {
echo 'You Pass!'
$grade = 'A';
}
</code> 

Using the **''Else''** keyword, you can execute a second set of code to execute when the condition is **not** met.  This allows you to perform two separate actions based on a single condition.  An example of this is shown below...

<code php>
// if-else statement
if ($score >= 60) {
echo 'You Pass!';
} else {
echo 'Sorry, You Failed';
}

// if-else as a single line statement
if ($score >= 60) echo 'You Pass!' else 'Sorry, You Failed';
</code>

Finally, the **''ElseIf''** keyword allows you to group multiple conditions into a ''If'' expression.  Using the scores example shown previously, we could display the grade for a student using the following conditional:

<code php>
// if-else statement
if ($score >= 90) {
	echo 'Grade: A';
} elseif ($score >= 80) {
	echo 'Grade: B';
} elseif ($score >= 70) {
	echo 'Grade: C';
} elseif ($score >= 60) {
	echo 'Grade: D';
} else {
	echo 'Sorry, You Failed';
}
</code>

You should take special notice of the evaluation order for your conditionals.  They are always done from top to bottom.  Once a single condition is met, **only the code for that condition will be executed**, all other conditions will be skipped.

==== Switch Statement ====

As an alternative to writing a series of **''elseif''** statements, you can use a **''switch''** statement to match a set of distinct values.

<code php>
switch ($grade) {
case 'A' : echo 'Excellent!';
	break;
case 'B' : echo 'Great!';
	break;
case 'C' : echo 'Good Job';
	break;
case 'D' : echo 'Good Effort';
	break;
default: echo 'Thanks for Trying';
}
</code>

After the **''switch''** keyword, you put an expression in parentheses that you want to use in your comparisons.  Next a set of curly braces define a block of literal values which are tested to match the expression shown.  The first value which matches will be executed.

The **''break''** statement exits the entire ''switch'' statement.  Without it, the processor would continue trying to match other values even after the first match is found.  The special value **''default''** will match any other value besides the ones which are explicitly defined.

==== For Statement ====

Use the **''for''** statement to iterate over a list of items or to repeat a block of statements a specified number of times.  The **''for''** statement has the following syntax (which is borrowed from the C language):

<code php>
for (initializer; comparison; incrementer) {
  // php statements to repeat
}
</code>

The **initializer** is where you initialize your variable.  Basically, this represents your starting place or starting condition.  It usually assigns a variable a value (e.g.: ''$i = 1'').  The **comparison** statement is the condition under which your **for** loop should continue repeating.  As long as this expressions evaluates to a **true** statement, the loop will repeat.  The **incrementer** is an action to perform (usually incrementing a counter) after each repetition of the loop.

Now let's look at a very simple example of a **for** loop which counts from one to five:

<code php>
// count from one to five!
for ($i = 1; $i <= 5; $i++) {
  echo 'count = ' . $i . '<br>';
}
</code>

As you can see, the variable $i is initialized to one ($i = 1) in the **initializer**.  The **condition** (''$i <= 10'') can be read as: repeat the loop as long as ''$i <= 5''.  Finally, the **incrementer** advances the counter by one after each iteration of the loop.  The output of this code would be:

<code html>
count = 1
count = 2
count = 3
count = 4
count = 5
</code>