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Last updated: Sat, 27 Jan 2007

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# echo

(PHP 3, PHP 4, PHP 5)

echo -- Выводит одну или более строк

## 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().

add a note User Contributed Notes
echo
Jim Walker
13-Jan-2007 11:24
`Putting the constant value __LINE__ in debugging messages can save time locating the message line in your source. You can use the same message text in more than one location and the message will be unique. For example,
echo __LINE__.' My Array: '.$k.' = '.$v.'<br>';`
Meercat9
13-Dec-2006 08:12
`<table align=center>
<?
//Using Backslashes Does not Make the Quotation Marks Not Execute, Only Separates them From the Others.
echo "<tr align=center bgcolor=#1A1A1A onMouseOver=\"this.bgColor='#33333';\" onMouseOut=\"this.bgColor='#1A1A1A';\">"
?>
</table>
Which Can Work Similar if You Want to Store Some Java Incorporated HTML in a String Variable.
<?
$table = "<table align=\"center\">
$td = "<tr align=center bgcolor=#1A1A1A onMouseOver=\"this.bgColor='#33333';\" onMouseOut=\"this.bgColor='#1A1A1A';\">";
$td = "<td align=\"center\">";
echo "<$table \n $tr \n $td \n Hello </td>\n</tr>\n</table>"
?>`
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.`
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.`
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.`
add a note
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Last updated: Sat, 27 Jan 2007
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