print

Description

int print ( string arg )

Outputs arg. Returns 1, always.

print() is not actually a real function (it is a language construct) so you are not required to use parentheses with its argument list.

例子 1. print() examples
<?php print("Hello World"); print "print() also works without parentheses."; print "This spans multiple lines. The newlines will be output as well"; print "This spans\nmultiple lines. The newlines will be\noutput as well."; print "escaping characters is done \"Like this\"."; // You can use variables inside of a print statement $foo = "foobar"; $bar = "barbaz"; print "foo is $foo"; // foo is foobar // You can also use arrays $bar = array("value" => "foo"); print "this is {$bar['value']} !"; // this is foo ! // Using single quotes will print the variable name, not the value print 'foo is $foo'; // foo is $foo // If you are not using any other characters, you can just print variables print $foo; // foobar print <<<END This uses the "here document" syntax to output multiple lines with $variable interpolation. Note that the here document terminator must appear on a line with just a semicolon no extra whitespace! END; ?>

For a short discussion about the differences between print() and echo(), see this FAQTs Knowledge Base Article: http://www.faqts.com/knowledge_base/view.phtml/aid/1/fid/40

注: 由于这是一个语言结构而非函数，因此它无法被变量函数调用。

See also echo(), printf(), and flush().

add a note User Contributed Notes

vincent at bevort dot com
22-May-2006 03:36


Sometime there is no choice in using a single or double quote

ie when using special chars to format the output to make the HTML more readable you have to use the Double qoutes. Single quotes make PHP fotmat the '\n' as text

phpnet at i3x171um dot com
21-May-2006 10:41


I have written a script to benchmark the several methods of outputting data in PHP: via single quotes, double quotes, heredoc, and printf. The script constructs a paragraph of text with each method. It performs this construction 10,000 times, then records how long it took. In total, it prints 160,000 times and records 16 timings. Here are the raw results.



Outputted straight to browser--



Single quotes: 2,813 ms

...with concatenation: 1,179 ms

Double quotes: 5,180 ms

...with concatenation: 3,937 ms

heredoc: 7,300 ms

...with concatenation: 6,288 ms

printf: 9,527 ms

...with concatenation: 8,564 ms



Outputted to the output buffer--



Single quotes: 8 ms

...with concatenation: 38 ms

Double quotes: 8 ms

...with concatenation: 47 ms

heredoc: 17 ms

...with concatenation: 49 ms

printf: 54 ms

...with concatenation: 52 ms



A nice graph of the script's output can be found here:

http://i3x171um.com/output_benchmarks/ob.gif



So what should you choose to print your text? I found several things out writing this.



First, it should be noted that the print and echo keywords are interchangeable, performance-wise. The timings show that one is probably an alias for the other. So use whichever you feel most comfortable with.



Second, if you've ever wondered which was better, the definitive answer is single quotes. Single quotes are at least four times faster in any situation. Double quotes, while more convenient, do pose a debatably significant performance issue when outputting massive amounts of data.



Third, stay away from heredoc, and absolutely stay away from [s]printf. They're slow, and the alternatives are there.



The source of my script can be found here:

http://i3x171um.com/output_benchmarks/ob.txt



DO NOT RUN THE SCRIPT ON THE INTERNET! Run it instead from localhost. The script outputs ~45 megabytes of text in an html comment at the top of the page by default. Expect the benchmark to take ~45 seconds. If this is too long, you can change the amount of iterations to a lower number (the results scale accurately down to about 1,000 iterations).

g8z at yahoo dot com
14-Mar-2006 03:16


I wanted to print a file on a Windows 2003 server from PHP, and found the "print" function instead. Just in case some other users are trying to physically print to a printer, rather than print to the screen, here's a function to do it.



This function will print a single file of one of these types: pdf, doc, xls, rtf, or plain text. If you have the full .exe path, you can print other document types, too. The shell_exec function is not enabled in safe mode.



Courtesy of Darren's Script Archive: http://www.tufat.com



<?php



function print_file($filename)

{

    // path to your adobe executable

    $adobe_path='"C:/Program Files/Adobe/Acrobat 7.0/Reader/AcroRd32.exe"';



    $ext='';

    $ext=strrchr($filename,'.');

    $ext=substr($ext,1);

    $ext_xl=substr($ext,0,2);



    if ($ext=='pdf') {

        shell_exec ($adobe_path.' /t '.$filename);

    }

    else if ($ext=='doc'||$ext=='rtf'||$ext=='txt') {

        $word = new COM("Word.Application");

        $word->visible = true;

        $word->Documents->Open($filename);

        $word->ActiveDocument->PrintOut();

        $word->ActiveDocument->Close();

        $word->Quit();

    }

    else if ($ext_xl=='xl') {

        $excel = new COM("Excel.Application");

        $excel->visible = true;

        $excel->Workbooks->Open($filename);

        $excel->ActiveWorkBook->PrintOut();

        $excel->ActiveWorkBook->Close();

        $excel->Quit();

    }

}



// example of printing a PDF



print_file("C:/photo_gallery.pdf");



?>

hw{}cho.de
07-Feb-2006 12:05


@jon: you have to use "ob_flush()" before "flush()" - see notes there.

jon at tap dot net
06-Dec-2005 05:48


I have a small utility run from the command line that processes a potentially huge list of files. As it can take hours to complete, I stuck a  



print '.';



statement in the body of the main loop to prove that something was  happening.



For reasons unknown to me, the utiliity suddenly started buffering the output such that it printed nothing until completion, defeating the purpose of the running monitor. Adding flush() statements did nothing. The problem was solved by using



fputs(STDOUT, '.');



but I have no idea why.

james-web at and dot org
26-Jul-2005 06:47


Note that if you want to dump the value of a variable, you want to use print_r(), var_dump() or var_export().

ejallison at gmail dot com
17-Jul-2005 06:10


This is a simple function for printing debug comments that I didn't think of for a long time. Maybe it'll serve you good too.



<?php



function printd($str) {

  if ($debug) { echo $str; }

}



// ...



if ($valueCalculatedEarlierInTheScript == 3) {

  doSomethingWithNoOutput();

  printd("doSomethingWithNoOutput() has executed.");

}



?>



It's mostly just to make sure everything is running without having to go through everything and put in echo "Step #whatever has executed" whenever something mysterious isn't working.

gem at rellim dot com
05-Nov-2004 05:28


HERE Documents can reference arrays as long as you enclose


the vars in {}.





Like this:





<?php





$line = array( 'title' => "Hello", 'date' => 'Today');





echo <<<EOT


Title: {$line['title']}


Date: {$line['date']}


EOT;





?>





Run this and get


Title: Hello


Date: Today





More info here, scroll down to "heredoc syntax":


http://www.php.net/manual/en/language.types.string.php

rjl at xs4all dot nl
16-Jan-2004 08:08


To elaborate on above example adding an


array variable


$text = <<<END


This uses the "here document" syntax to output


multiple lines with $variable interpolation. Note


that the here document terminator must appear on a


line with just a semicolon no extra whitespace!


User = {$_REQUEST['user']}


END;





'print $text;' Will output the string. Very handy for storing HTML.


Or adding {} around the array will allow you to use


above mentioned html blocks in conjuction with forms.





Rene =<>=

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