hemanman at gmail dot com, the problem is that func() doesn't actually return a value (string or otherwise), so the result of echoing func() is null.
With the comma version, each argument is evaluated and echoed in turn: first the literal string (simple), then func(). Evaluating a function call obviously calls the function (and in this case executes its own internal echo), and the result (null) is then echoed accordingly. So we end up with "outside func() within func()" as we would expect.
Thus:
<?php
echo "outside func ()\n", func ();
?>
effectively becomes:
<?php
echo "outside func ()\n";
//func ()
{
echo "within func ()\n";
}
echo '';
?>
The dot version is different: there's only one argument here, and it has to be fully evaluated before it can be echoed as requested. So we start at the beginning again: a literal string, no problem, then a concatenator, then a function call. Obviously the function call has to be evaluated before the result can be concatenated with the literal string, and THAT has to happen BEFORE we can complete the echo command. But evaluating func() produces its own call to echo, which promptly gets executed.
Thus:
<?php
echo "outside func ()\n" . func ();
?>
effectively becomes:
<?php
//func ()
{
echo "within func ()\n";
}
echo "outside func ()\n" . '';
?>
echo
(PHP 4, PHP 5)
echo — 1 つ以上の文字列を出力する
説明
void echo
( string
$arg1
[, string $...
] )すべてのパラメータを出力します。
echo は実際には関数ではありません (言語構造です)。このため、使用する際に括弧は必要ありません。 (いくつかの他の言語構造と異なり) echo は関数のように動作しません。そのため、 関数のコンテキスト中では常に使用することができません。 加えて、複数のパラメータを指定して echo をコールしたい場合、括弧の中にパラメータを記述してはいけません。
echo には、開始タグの直後に等号を付ける短縮構文もあります。 この短縮構文は、PHP 5.4.0 より前のバージョンでは設定オプションshort_open_tag が有効な場合しか使えません。
I have <?=$foo?> foo.
パラメータ
-
arg1 -
出力したいパラメータ。
-
... -
返り値
値を返しません。
例
例1 echo の例
<?php
echo "Hello World";
echo "This spans
multiple lines. The newlines will be
output as well";
echo "This spans\nmultiple lines. The newlines will be\noutput as well.";
echo "Escaping characters is done \"Like this\".";
// echo 命令の中で変数を使用することが可能です
$foo = "foobar";
$bar = "barbaz";
echo "foo is $foo"; // foo is foobar
// 配列を使用することもできます
$baz = array("value" => "foo");
echo "this is {$baz['value']} !"; // this is foo !
// 値ではなく変数名を出力するシングルクオートを使用します
echo 'foo is $foo'; // foo is $foo
// 他の文字を全く使用しない場合、echo 変数を使用可能です
echo $foo; // foobar
echo $foo,$bar; // foobarbarbaz
// 複数のパラメータを結合してechoに渡そうとする人もいます
echo 'This ', 'string ', 'was ', 'made ', 'with multiple parameters.', chr(10);
echo 'This ' . 'string ' . 'was ' . 'made ' . 'with concatenation.' . "\n";
echo <<<END
This uses the "here document" syntax to output
multiple lines with $variable interpolation. Note
that the here document terminator must appear on a
line with just a semicolon. no extra whitespace!
END;
// echo は関数のように動作しないので、以下のコードは正しくありません
($some_var) ? echo 'true' : echo 'false';
// しかし、次の例は動作します
($some_var) ? print 'true' : print 'false'; // print も言語構造ですが、
// 関数のように動作します。なので、
// このコンテキスト中で使用できます
echo $some_var ? 'true': 'false'; // 命令を変更
?>
注意
注意: これは、関数ではなく 言語構造のため、可変関数 を用いて コールすることはできません。
add a note
User Contributed Notes 10 notes
nikolaas dot mennega at links dot com dot au ¶
6 years ago
doydoy44 ¶
3 months ago
apparently ',' is faster then '.'
<?php
function f1_virgule() {
$a = '';
for($i=0; $i<100000; ++$i) {
echo $a,$i,"\n";
}
}
function f2_point() {
$a = '';
for($i=0; $i<100000; ++$i) {
echo $a.$i."\n";
}
}
$start = microtime(true);
f2_point();
$stop = microtime(true);
$time_point = $stop - $start;
$start = microtime(true);
f1_virgule();
$stop = microtime(true);
$time_virgule = $stop - $start;
echo 'time virgule : ' . $time_virgule . "\n";
echo 'time point : ' . $time_point . "\n";
echo 'time virgule > time time_point => ' . ($time_virgule > $time_point);
?>
-------------------------------------
time virgule : 18.28688621521
time point : 17.781190156937
time virgule > time time_point => 1
ximlabz at gmail dot com ¶
2 years ago
A remedy to the problems caused by different management of returns between different platforms you can use the predefined constant PHP_EOF as the second parameter:
<?php
$foo = "foo";
$bar = "bar";
echo "Foo is $foo", PHP_EOL;
echo "Bar is $bar";
// is the same as using:
echo "Foo is $foo\n";
echo "Bar is $bar";
// but here only for UNIX-like platforms
?>
Jason Carlson - SiteSanity ¶
8 years ago
In response to Ryan's post with his echobig() function, using str_split wastes memory resources for what you are doing.
If all you want to do is echo smaller chunks of a large string, I found the following code to perform better and it will work in PHP versions 3+
<?php
function echobig($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);
}
}
?>
ryan at wonko dot com ¶
8 years ago
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;
}
?>
fire at dls dot net ¶
2 years ago
Pay attention to this part of the documentation:
echo() (unlike some other language constructs) does not behave like a function, so it cannot always be used in the context of a function
I was trying to make certain that I was detecting errors and was trying code like this:
@alwaysFails() or echo('Surprise! It failed again');
This error was generated:
[29-Jul-2011 12:56:19] PHP Parse error: syntax error, unexpected T_ECHO in /Applications/MAMP/test.php on line 12
Changing to die(), print() or a function I defined worked fine. Beware of this limitation of echo.
gbarros at yahoo-inc dot com ¶
3 years ago
just banged my head on this missing bits on the manual.
When using the <<< method, the array keys does not require any kind of quotes.
<?php
foreach ( $data as $i ){
echo <<< END
<tr>
<td>$i[date]</td>
<td>$i[name]</td>
</tr>
END;
}
?>
Let's hope you don't have any <?php echo $klingonships['th\'bl][ath']?> kind of array :)
Jakob Thomsen ¶
5 years ago
A way to color your echo output is to use shell_exec and the echo command (this only works on Linux/bash) in the following way:
<?php
echo shell_exec('echo "\e[0;31m Red color \e[0;32mGreen color \e[0m No color "');
?>
See http://wiki.archlinux.org/index.php/Color_Bash_Prompt for more colors and other options.
Sammy Moshe ¶
9 months ago
And if you wanted to, you could do something like
echo "test1","test2","test3";
I'm not sure how it's useful. Might be good if you have a bunch of strings you want to output at once, but it doesn't seem to work with arrays. I'm working on a practical application, but as yet haven't had a need for it.
zombie)at(localm)dot(org) ¶
10 years ago
[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.