Learn more about php4(1)--Back to the Future_PHP Tutorial

For those readers who are unfamiliar with this concept, a loop is a control structure that allows you to reuse the same series of PHP commands over and over again. The actual number of repetitions can be decided by you.

The first and simplest loop is the so-called "while" loop, as shown below:

while (condition)
{
do this!
}

Or, in Chinese

while (it’s raining)
{
Bring an umbrella!
}

In this case , as long as the value of the condition is true, remember what you learned last time? ---The PHP commands in curly brackets will always be executed. As soon as the condition becomes false - for example, in the above example, the sun comes out, the loop will terminate and subsequent commands will not be executed.

Here is a simple example to illustrate how to use a "while" loop:



< ?

// If the form has not been submitted yet, Display initialization page
if (!$submit)
{
?>

< html>

< head>
< /head>

< body>
< h2>Incredibly wonderful time machine< /h2>
< form action="tmachine.php" method ="POST">
In which year do you plan to visit?
< input type="text" name="year" size="4" maxlength="4">
< input type="submit" name="submit" value="Go">
< /form>
< /body>
< /html>

< ?
}
else
// Otherwise, it will be processed and a new page will be generated
{
?>

< html>

< head>
< /head>

< body>

< ?
//The current year
$current = 2001;

// Check the future time and generate the corresponding information


In this example, we first ask the user for the year he wishes to access - the year is stored in the variable year , and sent to the PHP script.

The script first checks the year to make sure it is in the past [haha, we seem to be doing this ourselves now] and then uses a "while" loop to calculate backwards from the current year - 2001 and store the result in the variable current until the values ​​of $current and $year are the same.

Please note that we use the submit variable to generate both an initialization form and a processing page on the same PHP page - we have already explained this technology to you in detail last time.​

http://www.bkjia.com/PHPjc/315766.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/315766.htmlTechArticleFor those readers who are not familiar with this concept, a loop is a method that allows you to reuse the same series over and over again Control structure of PHP commands. The actual number of repetitions can be decided by you. ...