How are \r \t and \n different from one another? [duplicate]

问题

In the code below, I don't know how these characters are different functionally from one another: \r \t \n. Does anyone have an explanation or description for these?

Here is some sample code:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
    <head>
        <title>Sorting words in a block of text by length</title>
        <link rel="stylesheet" type="text/css" href="common.css" />
    </head>
    <body>
        <h1>Sorting words in a block of text by length</h1>

<?php

$myText = <<<END_TEXT
But think not that this famous town has 
only harpooneers, cannibals, and 
bumpkins to show her visitors. Not at 
all. Still New Bedford is a queer place. 
Had it not been for us whalemen, that 
tract of land would this day perhaps 
have been in as howling condition as the 
coast of Labrador.
END_TEXT;

echo "<h2>The text:</h2>";
echo "<div style=\"width: 30em;\">$myText</div>";

$myText = preg_replace( "/[\,\.]/", "", $myText );
$words = array_unique( preg_split( "/[ \n\r\t]+/", $myText ) );
usort( $words, create_function( '$a, $b', 'return strlen($a) - strlen($b);
' ) );

echo "<h2>The sorted words:</h2>";
echo "<div style=\"width: 30em;\">";

foreach ( $words as $word ) {
    echo "$word ";
}
echo "</div>";

?>
    </body>
</html>

回答1:

\n is a symbol for new line

\t is a symbol for tab

and \r is for 'return'

You can find more information here: What is the difference between \r and \n?

回答2:

The \n symbol means literally new line. This will go to the start of the next new line.

The \t symbol means add a tab (which is usually 4 spaces but can easily be 2 or 8 depending on the context).

The \r symbol is no more used that often. It means carriage return which means go to the start of the line. It was used together with \n for being sure even "old" printers would get to the beginning of the next line.

来源：https://stackoverflow.com/questions/15423001/how-are-r-t-and-n-different-from-one-another

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