PHP: echo - Manual

Описание

void echo ( string arg1 [, string argn...] )

Выводит все аргументы.

На самом деле echo() - это не функция, а конструкция языка, поэтому заключать аргументы в скобки не обязательно, даже при использовании нескольких аргументов.

Пример 1. Примеры использования echo()

<?php echo "Привет мир!"; echo "Это занимет несколько строк. Переводы строки тоже выводятся"; echo "Это занимет\nнесколько строк. Переводы строки тоже\nвыводятся"; echo "Экранирование символов делается \"Так\"."; // с echo можно использовать переменные ... $foo = "foobar"; $bar = "barbaz"; echo "foo - это $foo"; // foo - это foobar // ... и массивы $bar = array("value" => "foo"); echo "это {$bar['value']} !"; // это foo ! // При использовании одиночных кавычек выводится // имя переменной,а не значение echo 'foo - это $foo'; // foo - это $foo // можно вывести просто значения переменных echo $foo; // foobar echo $foo,$bar; // foobarbarbaz // Некоторые предпочитают передачу нескольких аргументов // вместо конкатенации echo 'Эта ', 'строка ', 'была ', 'создана ', 'несколькими параметрами.', chr(10); echo 'Эта ' . 'строка ' . 'была ' . 'создана ' . 'с помощью конкатенации.' . "\n"; echo <<<END Здесь используется синтаксис "here document" для вывода нескольких строк с подстановкой переменных $variable. Заметьте,что закрывающий идентификатор должен располагаться в отдельной строке. никаких пробелов! END; // Следующая строка неверна, так как echo не является функцией ($some_var) ? echo 'true' : echo 'false'; // Но это можно записать по другому ($some_var) ? print('true'): print('false'); // print является функцией echo $some_var ? 'true': 'false'; // echo вынесен за пределы выражения ?>

echo() имеет также краткую форму, представляющую собой знак равенства, следующий непосредственно за открывающим тэгом. Этот сокращенный синтаксис допустим только когда директива конфигурации short_open_tag включена.


I have <?=$foo?> foo.

Различия между print() и echo() рассматриваются в этой статье: http://www.faqts.com/knowledge_base/view.phtml/aid/1/fid/40

Замечание: Поскольку это языковая конструкция, а не функция, она не может вызываться при помощи переменных функций

См. также описания функций print(), printf(), и flush().

echo

phpnet at i3x171um dot com
20-May-2006 07:39


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).

bennyhur at gmail dot com
01-Feb-2006 11:39


in response to:



"This is a beauty for lots of text, really.  And easy to read, if you're a PERL or shell person." 



If you use an editor like Dreamweaver that can show you a somewhat rendered version of the page, you can output large blocks of text/html by doing the following:



<?php

if(boolean_function())

{

?>

   <p>You successfully made the boolean funciton return true</p>

   <p>blah blah blah....</p>

<?php

}

else

{

?>

   <p>Sorry, but you didnt make the boolean true!</p>

<?php

}

//more code...

?>



As opposed to using the "dochere" syntax. I find it's much easier to move around in large scripts when I output HTML like this because I can just click on the text near the code I need to edit in Dreamweavers display view, and then switch to code view and I'm right were I need to be.

rwruck
27-Jan-2006 01:15


It should be mentioned here that the script will be aborted if you output something in response to a HTTP HEAD request.

In the following example, the second line will NOT be written to the file. Any registered shutdown function will be called, though:



<?php

$hf = fopen('head.log', 'ab');

fwrite($hf, "before output\n");

echo "Test";

fwrite($hf, "after output\n");

fclose($hf);

?>



This is normal behaviour; see the description of $_SERVER.

the dot only dot storm at gmail dot com
06-Jan-2006 12:38


In reply to lorenpr at gmail dot com:

"I hope this ternary thing isn't overkill. Last thing - I would just like to make you aware of the side effect when you do this statement,

 

<?php

echo $some_var ? print 'true': print 'false';

?>



The result would be either 'true1' or 'false1', depending on whether $some_var is true or false respectively. This happens because of what I mentioned earlier. Figure it out."



The reason it prints the 1 because whether the variable is true or false, in this case, print will always return 1 (true)



Meaning this is the same thing:

<?php

echo print($some_var ? 'true' : 'false');

?>



print($some_var ? 'true' : 'false') = 1

So you echo 1, after the print takes place.

07-Oct-2005 01:09


This is a beauty for lots of text, really.  And easy to read, if you're a PERL or shell person.



echo <<<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;

lorenpr at gmail dot com
14-Sep-2005 09:12


I hope this ternary thing isn't overkill. Last thing - I would just like to make you aware of the side effect when you do this statement, 

 

echo $some_var ? print 'true': print 'false';



The result would be either 'true1' or 'false1', depending on whether $some_var is true or false respectively. This happens because of what I mentioned earlier. Figure it out.

lorenpr at gmail dot com
14-Sep-2005 08:58


linus is correct.

The ternary relationship is evaluated first, then echo prints the result.



Also, keep in mind

(condition? a : b) 

reads 

if(condition) return a; else return b;



So what makes 

A. echo ($somevar) ? 'true' : 'false';



different from



B. ($somevar) ? echo 'true' : echo 'false';



is the ternary relationship in A reads

if (condition) return 'true'; else return 'false';



while in B it reads

if(condition) return (echo 'true'); else return (echo 'false');



- an invalid statement, since echo evaluates to void.

linus.martensson a gmail
24-Aug-2005 02:03


Simple. it reads like echo (($somevar)?'true';'false'); and outputs the result, unless I'm mistaken.

shannonmoeller at gmail dot com
09-Aug-2005 04:31


In reply to lorenpr at gmail dot com:



If what you say is true, why does this work?



<?php

echo ($somevar) ? 'true' : 'false'; //works

?>

lorenpr at gmail dot com
28-Jul-2005 10:17


I just want to point out something to beginners. The documentation is misleading where it says:



// Because echo is not a function, following code is invalid.

($some_var) ? echo 'true' : echo 'false';



The code is invalid, but not because 'echo' is a language construct, but rather because 'echo' does not return a value. 

So don't be mislead: the syntax used above is certainly not limited to functions.



You must keep in mind that the job of the ternary syntax used is not actually to display anything, but to test a boolean relationship. The 'print' statement would work because it always returns a 1, which in php, is interpreted to a boolean  'true'. Things that return 'void' cannot be expected to evaluate to a 'true' or 'false', and that is why using 'echo' in this particular case is invalid.

Jason Carlson - SiteSanity
16-May-2005 10:28


In response to Ryan's post with his echobig() function, using str_split wastes memory resources for what you are doing. 



If all you want to do is echo smaller chunks of a large string, I found the following code to perform better and it will work in PHP versions 3+



<?php

function echobig($string, $bufferSize = 8192)

{

  // suggest doing a test for Integer & positive bufferSize

  for ($chars=strlen($string)-1,$start=0;$start <= $chars;$start += $bufferSize) {

    echo substr($string,$start,$buffer_size);

  }

}

?>

renrutal at gmail dot com
28-Mar-2005 03:34


Note that:



<?php

echo "2 + 2 = " . 2+2; // This will print 4

echo "2 + 2 = " , 2+2; // This will print 2+2 = 4

?>



The commas will parse the result of the expressions correctly.

paul dot mateescu at zirkonmedia dot ro
27-Feb-2005 02:35


Hello, 



If you want to use echo <<<ENDOFECHO (here document style) and you notice that the server does not seem to recognise this form (you get a blank page with no content at all), chances are your editor uses a wrong type of line break. 



Fore instance, I use Dreamweaver for Macintosh. You should have the following preferences: 



Dreamweaver >> Preferences >> Code Format >> Line break type



set to "CR LF (Windows)" or "LF (Unix)". Dreamweaver for Mac ships with "CR (Macintosh)" by default (at least the MX edition, don't know about any other editions), which confuses the PHP interpreter. 



Best,



Paul Mateescu

ryan at wonko dot com
27-Feb-2005 12:56


Due to the way TCP/IP packets are buffered, using echo to send large strings to the client may cause a severe performance hit. Sometimes it can add as much as an entire second to the processing time of the script. This even happens when output buffering is used.



If you need to echo a large string, break it into smaller chunks first and then echo each chunk. The following function will do the trick in PHP5:



<?php

function echobig($string, $bufferSize = 8192)

{

    $splitString = str_split($string, $bufferSize);



    foreach($splitString as $chunk)

        echo $chunk;

}

?>

Truffy
15-Jan-2005 01:02


You can use braces around variables as well as array items. This is useful to help recognition of your variables in your code, but most useful where the variable iteslf cannot be separated with spaces from the preceding/following code, for exmple in a file path:



If a path is assigned the variable $path, then this code will not work:



echo "$pathindex.php";



whereas this will



echo "{$path}index.php";

zombie)at(localm)dot(org)
25-Jan-2003 11:26


[Ed. Note: During normal execution, the buffer (where echo's arguments go) is not flushed (sent) after each write to the buffer. To do that you'd need to use the flush() function, and even that may not cause the data to be sent, depending on your web server.]





Echo is an i/o process and i/o processes are typically time consuming. For the longest time i have been outputting content by echoing as i get the data to output. Therefore i might have hundreds of echoes in my document. Recently, i have switched to concatenating all my string output together and then just doing one echo at the end. This organizes the code more, and i do believe cuts down on a bit of time. Likewise, i benchmark all my pages and echo seems to influence this as well. At the top of the page i get the micro time, and at the end i figure out how long the page took to process. With the old method of "echo as you go" the processing time seemed to be dependent on the user's net connection as well as the servers processing speed. This was probably due to how echo works and the sending of packets of info back and forth to the user. One an one script i was getting .0004 secs on a cable modem, and a friend of mine in on dialup was getting .2 secs. Finally, to test that echo is slow; I built strings of XML and XSLT and used the PHP sablotron functions to do a transformation and return a new string. I then echoed the string. Before the echo, the process time was around .025 seconds and .4 after the echo. So if you are big into getting the actual processing time of your scripts, don't include echoes since they seem to be user dependent. Note that this is just my experience and it could be a fluke.