print

(PHP 4, PHP 5)

print文字列を出力する

説明

int print ( string $arg )

arg を出力します。

printは実際には関数ではありません (言語構造です)。このため、引数を括弧で括る必要はありません。

パラメータ

arg

入力データ。

返り値

常に 1 を返します。

例1 print の例

<?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\".";

// print文の中で変数を使用することが可能です。
$foo "foobar";
$bar "barbaz";

print 
"foo is $foo"// foo is foobar

// 配列も使用可能です。
$bar = array("value" => "foo");

print 
"this is {$bar['value']} !"// this is foo !

// シングルクオートを使用すると値ではなく変数名が出力されます。
print 'foo is $foo'// foo is $foo

// 他の文字を使用しない場合、変数だけを出力することが可能です。
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;
?>

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。

参考

add a note add a note

User Contributed Notes 14 notes

up
11
user at example dot net
6 years ago
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
   
}
?>
up
6
ejallison at gmail dot com
9 years ago
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.
up
4
jon
7 years ago
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)
up
2
Chris Watson
5 years ago
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.
up
3
http://www.danielxmorris.com
6 years ago
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;
    }

?>
up
3
gem at rellim dot com
9 years ago
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
up
1
danielxmorris @ gmail dotcom
6 years ago
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
up
2
Luke Wenke
1 year ago
"print is not actually a real function (it is a language construct) so you are not required to use parentheses with its argument list."

I don't think it has an "argument list" because the following gives a syntax error:

print (1, 2);

Here is an example of how the brackets work with print:

print ((1) + (2)) + (3);

Unlike a function it doesn't just use the first brackets... it prints "9".
up
1
mvpetrovich
7 years ago
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>");

?>
up
0
user at example dot net
6 years ago
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
   
}
?>
up
0
phpnet at i3x171um dot com
8 years ago
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).
up
0
jon at tap dot net
8 years ago
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.
up
0
james-web at and dot org
9 years ago
Note that if you want to dump the value of a variable, you want to use print_r(), var_dump() or var_export().
up
-4
aflavio at gmail dot com
3 years ago
Check this statement:

echo 3 . print(2) . print(4) . 5 . 'c' . print(6) . print(7). 'b' .print(8) . 'a';

It's will always output starting from the right to the left.

Thus we have:

8a                              //1o print
7b18a                        //2o print
617b18a                    //3o print
8a7b16145c1             //4o print

8a7b16145c12131     //Final output

That's it.
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