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(PHP 4, PHP 5)
print — Ausgabe eines Strings
Gibt arg aus.
print() ist keine wirkliche Funktion (sondern ein Sprachkonstrukt), weshalb Sie beim Aufruf nicht unbedingt Klammern um die Argumentliste setzen müssen.
Die Eingabedaten.
Gibt immer 1 zurück.
Beispiel #1 print()-Beispiele
<?php
print("Hallo Welt");
print "print() funktioniert auch ohne Klammern.";
print "Dies umfasst
mehrere Zeilen. Die Zeilenumbrüche werden
ebenfalls ausgegeben";
print "Dies umfasst\nmehrere Zeilen. Die Zeilenumbrüche werden\nebenfalls ausgegeben.";
print "Escape-Zeichen werden \"so\" geschrieben.";
// Sie können in einer print-Anweisung auch Variablen benutzen
$foo = "foobar";
$bar = "barbaz";
print "foo ist $foo"; // foo ist foobar
// Sie können auch Arrays verwenden
$bar = array("value" => "foo");
print "Das ist {$bar['value']} !"; // Das ist foo !
// Einfache Anführungsstriche geben den Variablennamen aus, nicht den Inhalt
print 'foo ist $foo'; // foo ist $foo
// Benutzen Sie keine anderen Zeichen, können Sie auch nur
// Variablen ausgeben
print $foo; // foobar
print <<<END
Dies verwendet die "here document" Syntax zur Ausgabe von
mehreren Zeilen mit $Variablen-Interpolation. Beachten Sie,
dass das "here document" Endezeichen in einer Zeile nur mit
einem Semikolon ohne Whitespaces stehen muss!
END;
?>
Hinweis: Da dies ein Sprachkonstrukt und keine Funktion ist, können Sie dieses nicht mit Variablenfunktionen verwenden.
Printing an empty string from PHP, as in
print "";
returns a single byte (content length=1) - the line-feed character '\n' (0a).
So if you truly want to return an empty string, you may want to use "flush()" instead - then headers without any Content-length will be returned.
Do note, however, that regardless of whether print or flush is used, accessing such a PHP output from AJAX (via .responseText) will always have a '\n' as a value for an "empty" string sent from PHP.
mvpetrovich of 2007 could just use single quotes as his string delimiters (see the example in the current documentation).
It's not ALWAYS appropriate, but generally it is best (the Zend Framework coding standards have a good take on this). It yields a number of interesting benefits:
1: Nobody will be tempted to write functions to replace backticks or other characters with double quotes. Such functions may cause a (negligible) loss of efficiency, and maybe other undesired effects.
2: You will be able to use double quotes without escaping. This is recommended (although not required) for HTML and XML attributes, as well as quoted text.
3: The script will hit the browser very slightly slightly faster since PHP doesn't have to scan through the string looking for variables, escaped characters, curly braces or other things.
4: Your code gets ten times easier to read. (as mvpetrovich pointed out)
If, in spite of these four excellent benefits, you really MUST still use double quotes to delimit boring old string constants (and seriously, why would you?), you could use the slightly less favourable single quotes as delimiters for most markup languages.
HTML served as HTML will even let you lay out unquoted attributes (yuck).
It should also be noted though that if you are just printing bare strings, you may as well shut off the php parser. The quickest way to send a string is to write it as plain text, OUTSIDE of the php tags. This will also make your code look excellent in a lot of syntax highlighters.
There are few disadvantages to doing this, if any. Output buffering still works. All your classes and objects and includes remain in place. Your script runs faster. World peace is obtained.
An update to the println function I wrote below, this is a more efficient, correct and returns a value (1, always; (print)).
<?php
function println($string_message = '') {
return isset($_SERVER['SERVER_PROTOCOL']) ? print "$string_message<br />" . PHP_EOL:
print $string_message . PHP_EOL;
}
?>
Be careful when using print. Since print is a language construct and not a function, the parentheses around the argument is not required.
In fact, using parentheses can cause confusion with the syntax of a function and SHOULD be omited.
Most would expect the following behavior:
<?php
if (print("foo") && print("bar")) {
// "foo" and "bar" have been printed
}
?>
But since the parenthesis around the argument are not required, they are interpretet as part of the argument.
This means that the argument of the first print is
("foo") && print("bar")
and the argument of the second print is just
("bar")
For the expected behavior of the first example, you need to write:
<?php
if ((print "foo") && (print "bar")) {
// "foo" and "bar" have been printed
}
?>
Be careful when using print. Since print is a language construct and not a function, the parentheses around the argument is not required.
In fact, using parentheses can cause confusion with the syntax of a function and SHOULD be omited.
Most would expect the following behavior:
<?php
if (print("foo") && print("bar")) {
// "foo" and "bar" had been printed
}
?>
But since the parenthesis around the argument are not required, they are interpretet as part of the argument.
This means that the argument of the first print is
("foo") && print("bar")
and the argument of the second print is just
("bar")
For the expected behavior of the first example, you need to write:
<?php
if ((print "foo") && (print "bar")) {
// "foo" and "bar" had been printed
}
?>
I wrote a println function that determines whether a \n or a <br /> should be appended to the line depending on whether it's being executed in a shell or a browser window. People have probably thought of this before but I thought I'd post it anyway - it may help a couple of people.
<?php
function println ($string_message) {
$_SERVER['SERVER_PROTOCOL'] ? print "$string_message<br />" : print "$string_message\n";
}
?>
Examples:
Running in a browser:
<?php println ("Hello, world!"); ?>
Output: Hello, world!<br />
Running in a shell:
<?php println ("Hello, world!"); ?>
Output: Hello, world!\n
the FAQTs article can be found archived at http://web.archive.org/web/20060601063513/http
://www.faqts.com/knowledge_base/view.phtml/aid/1/fid/40
(url split to get past the line-length limitation)
I grew quite tired of backslashes, and wrote these routines. It uses the back single quote as a substitute for double quotes within a statement. It made my code much more readable. It is a little easier than using a "here document." I also found I make a few less typing errors.
<?php
function qq($text) {return str_replace('`','"',$text); }
function printq($text) { print qq($text); }
function printqn($text) { print qq($text)."\n"; }
//example - before
echo "<a href=\"#\" class=\"stdbutton\" style=\"float:left;\" onclick=\"myfunction(); return false;\">My Link</a>\n";
//becomes - with printqn function
printqn("<a href=`#` class=`stdbutton` style=`float:left;` onclick=`myfunction(); return false;`>My Link</a>");
?>
At the top of your page, do something to this effect:
<?php
$n = "\n";
$t = "\t";
?>
Then, if you need your table cell four tabs in:
<?php echo($t . $t . $t . $t . '<td>whatever</td>' . $n); ?>
This means the parser only has to interpret four characters inside double quotes, then just stores them in variables. With strings that small, concatenating six things together won't be slow at all.
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
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).
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();
$excel->Quit();
}
}
// example of printing a PDF
print_file("C:/photo_gallery.pdf");
?>
I have a small utility run from the command line that processes a potentially huge list of files. As it can take hours to complete, I stuck a
print '.';
statement in the body of the main loop to prove that something was happening.
For reasons unknown to me, the utiliity suddenly started buffering the output such that it printed nothing until completion, defeating the purpose of the running monitor. Adding flush() statements did nothing. The problem was solved by using
fputs(STDOUT, '.');
but I have no idea why.
Note that if you want to dump the value of a variable, you want to use print_r(), var_dump() or var_export().
This is a simple function for printing debug comments that I didn't think of for a long time. Maybe it'll serve you good too.
<?php
function printd($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.
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
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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