Page 97 - Beginning PHP 5.3

Chapter 4: Decisions and Loops
Doing Repetitive Tasks with Looping

You can see that the ability to make decisions — running different blocks of code based on certain
criteria — can add a lot of power to your PHP scripts. Looping can make your scripts even more
powerful and useful.

The basic idea of a loop is to run the same block of code again and again, until a certain condition is met.
As with decisions, that condition must take the form of an expression. If the expression evaluates to
true , the loop continues running. If the expression evaluates to false , the loop exits, and execution
continues on the first line following the loop ’ s code block.
You look at three main types of loops in this chapter:

❑ while loops
❑ do...while loops
❑ for loops

You explore foreach() loops, which work specifically with arrays, in Chapter 6 .

Simple Looping with the while Statement

The simplest type of loop to understand uses the while statement. A while construct looks very similar
to an if construct:
while ( expression ) {
// Run this code
}
// More code here

Here ’ s how it works. The expression inside the parentheses is tested; if it evaluates to true , the code
block inside the braces is run. Then the expression is tested again; if it ’ s still true , the code block is run
again, and so on. However, if at any point the expression is false , the loop exits and execution
continues with the line after the closing brace.

Here ’ s a simple, practical example of a while loop:
< ?php

$widgetsLeft = 10;
while ( $widgetsLeft > 0 ) {
echo “Selling a widget... “;

;
$widgetsLeft - -
echo “done. There are $widgetsLeft widgets left. < br / > ”;
}
echo “We ’ re right out of widgets!”;

? >

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