I've been developing with PHP for some years now, and recently came across this code:
<?php
echo <<<EOB
<html>
<head>
<title>My title</title>
</head>
...
EOB;
?>
I've never seen this approach to print HTML, which seems to be pretty useful and less prone to some weird variable or double quote syntax error.
I've searched for some official information about this and only found a post of Rasmus talking about this.
What is a detailed explanation about this functionality and what does EOB mean? Maybe end of block?
This is known as heredoc syntax. The documentation will tell you everything you need to know.
Essentially, however:
A third way to delimit strings is the heredoc syntax: <<<. After this operator, an identifier is provided, then a newline. The string itself follows, and then the same identifier again to close the quotation.
The closing identifier must begin in the first column of the line. Also, the identifier must follow the same naming rules as any other label in PHP: it must contain only alphanumeric characters and underscores, and must start with a non-digit character or underscore.
So EOB is just what the author chose as his delimiter, not really sure what it stands for in his case but the identifier can be whatever you want.
Just for the sake of completeness, Heredoc in PHP is inherited from Perl, which itself inherited it from the Bourne shell.
It´s called heredoc and is described in the manual.
The official term is 'here document' I believe, usually shortened to 'heredoc'.
This is called heredoc syntax. It lets you treat large blocks of text like a string. It allows for newlines as well. Variables can be inserted into the block of text, just like using the double quotation marks for strings.
A more useful explanation can be found on PHP's own website: http://php.net/manual/en/language.types.string.php
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I want to print "that's it!" Exactly as same with double and single quotations in php? Can anyone have solution?
You just have to escape the single quote with a back slash
echo '"that\'s it!"';
I'll post something different because I like them and it think it's often missed or unknown by less experienced programmers.
HereDoc/NowDoc
//HereDoc works like " for variables
echo <<<TXT
"that's it!"
TXT;
The TXT tag can be anything that follows the same rules as variable names (\w+, and must start with Alpha), and the ending one must be on it's own line with "ABSOULTLY" nothing else besides ; (which can be omitted in arrays), nothing else not even whitespaces.
//NowDoc works like ' for variables
echo <<<'TXT'
"that's it!"
TXT;
It's often overlooked, as it's not documented in any really visible place, it's the third example on the string type page on PHP.net. Then after a bunch of scrolling you'll find the Nowdoc part, the only real difference is how they treat variables, as I mentioned.
http://php.net/language.types.string#language.types.string.syntax.heredoc
A third way to delimit strings is the heredoc syntax: <<<. After this operator, an identifier is provided, then a newline. The string itself follows, and then the same identifier again to close the quotation.
The closing identifier must begin in the first column of the line. Also, the identifier must follow the same naming rules as any other label in PHP: it must contain only alphanumeric characters and underscores, and must start with a non-digit character or underscore.
Warning
It is very important to note that the line with the closing identifier must contain no other characters, except a semicolon (;). That means especially that the identifier may not be indented, and there may not be any spaces or tabs before or after the semicolon. It's also important to realize that the first character before the closing identifier must be a newline as defined by the local operating system. This is \n on UNIX systems, including macOS. The closing delimiter must also be followed by a newline.
If this rule is broken and the closing identifier is not "clean", it will not be considered a closing identifier, and PHP will continue looking for one. If a proper closing identifier is not found before the end of the current file, a parse error will result at the last line.
This is also common in other languages besides PHP (with minor variations), and it's the cleanest way (for larger amounts of text, think HTML, JavaScript and a mix of those and PHP).
$selector = 'a.foobar';
echo <<<HTML
<script type="text/javascript">
;( function( $, window, document, undefined ) {
"use strict";
$(document).ready(function(){
$('tr.foobar').css('display', 'none');//singe quotes are fine
$("div.foobar").css("display", "none");//double quotes are too
$({$selector}).css('display', "none");//we can even mix them up if we want.
//we can use PHP variable like {$selector}, even these
//comments become comments in the JS.
//if that wasn't enough, most IDE's treat them like HTML
//so they are not greyed out, but nicely colored!
});
} ) ( jQuery, window, document );
</script>
HTML;
And this would work just fine, even the {$selector} would be replaced by PHP, the {} are optional except for method calls (unless they changed that). I put them in by habit because it colors them better in my IDE. Which is excatly how PHP treats variables in "normal" double quoted strings. (variable interpolation) except here we can use both types of quotes any way we want to...
If you do ever put one in an array it will only work this way (without the ;):
$a = [
<<<TXT
sometext
TXT
, "something else",
1,
2,
'etc..'
];
Other languages that use them (linked to the PHP section)
https://en.wikipedia.org/wiki/Here_document#PHP
In computing, a here document (here-document, here-text, heredoc, hereis, here-string or here-script) is a file literal or input stream literal: it is a section of a source code file that is treated as if it were a separate file. The term is also used for a form of multiline string literals that use similar syntax, preserving line breaks and other whitespace (including indentation) in the text.
The important thing is it does not use the quotes to define the string, so you are free to use them however you want, with no escaping.
One last thing I happened to notice from the PHP documentation that i never really read before.
the first character before the closing identifier must be a newline as defined by the local operating system. This is \n on UNIX systems, including macOS
Maybe someone else knows, but I am not sure how important this bit really is. I program on a Windows Desktop \r\n, and then use the same exact files on a Linux server \n and Have Never 1 time had an issue with what that says. I do use editors though like Eclipse PDT, so it may default to the \n even on windows. But I have never had an issue on either one....
Enjoy!!
Probably one of the ways that works without escaping is as follows:
echo('"'."that'".'s it!"');
I've been developing with PHP for some years now, and recently came across this code:
<?php
echo <<<EOB
<html>
<head>
<title>My title</title>
</head>
...
EOB;
?>
I've never seen this approach to print HTML, which seems to be pretty useful and less prone to some weird variable or double quote syntax error.
I've searched for some official information about this and only found a post of Rasmus talking about this.
What is a detailed explanation about this functionality and what does EOB mean? Maybe end of block?
This is known as heredoc syntax. The documentation will tell you everything you need to know.
Essentially, however:
A third way to delimit strings is the heredoc syntax: <<<. After this operator, an identifier is provided, then a newline. The string itself follows, and then the same identifier again to close the quotation.
The closing identifier must begin in the first column of the line. Also, the identifier must follow the same naming rules as any other label in PHP: it must contain only alphanumeric characters and underscores, and must start with a non-digit character or underscore.
So EOB is just what the author chose as his delimiter, not really sure what it stands for in his case but the identifier can be whatever you want.
Just for the sake of completeness, Heredoc in PHP is inherited from Perl, which itself inherited it from the Bourne shell.
It´s called heredoc and is described in the manual.
The official term is 'here document' I believe, usually shortened to 'heredoc'.
This is called heredoc syntax. It lets you treat large blocks of text like a string. It allows for newlines as well. Variables can be inserted into the block of text, just like using the double quotation marks for strings.
A more useful explanation can be found on PHP's own website: http://php.net/manual/en/language.types.string.php
I am following a book tutorial where the author do like this to display html
eks:
return <<<ADMIN_OPTIONS
+ add a new event
<form action="assets/inc/process.inc.php" method="post">
<div>
<input type="submit" value="Log Out" class="admin" />
<input type="hidden" name="token" value="$_SESSION[token]" />
<input type="hidden" name="action" value="user_logout" />
</div>
</form>
ADMIN_OPTIONS;
I don't quite understand the <<<, from my understanding you can call ADMIN_OPTIONS whatever as long as you end the html with the same words. The thing I really don't understand though is when I write ADMIN_OPTIONS; and all my code goes in comment mode. For example:
The above example works, this does not:
return <<<ADMIN_OPTIONS
Log In
ADMIN_OPTIONS;
but this works:
return <<<ADMIN_OPTIONS
Log In
ADMIN_OPTIONS;
As others mentioned, this is called heredoc.
You can choose the identifier freely. It's very similar to using double quotes, you can embedd variables with {$var} too. Because of that you also can't use them in any static context, like a default value in a class, consts or define()s. That's why nowdocs were introduced (in PHP 5.3).
If you read the manual entry, you'll quickly find out why your example doesn't work; there
must not be any spaces or tabs in front of the ending identifier.
From the manual:
It is very important to note that the
line with the closing identifier must
contain no other characters, except
possibly a semicolon (;). That means
especially that the identifier may not
be indented, and there may not be any
spaces or tabs before or after the
semicolon. It's also important to
realize that the first character
before the closing identifier must be
a newline as defined by the local
operating system.
It's Heredoc. Not usually used often.
I think your second example doesn't work because the end identifier line is not "clean". There's a space after the semicolon, whereas the first and third examples are clean.
The syntax you are using is called heredoc, and it is explained in the following section of the PHP manual:
http://php.net/manual/en/language.types.string.php
Basically all it is is an alternative to encapsulating strings within quotes.
These are exactly the same as:
return "
foo bar
";
The difference is that you can specify the termination character sequence yourself, i.e. you're not limited to quotes to start and end your string.
return <<<TERMINATIONSEQUENCE
Because I'm not limited to "quotes",
I can 'freely' use them in "this 'string"'
without worrying about escaping them!
TERMINATIONSEQUENCE;
This is called Heredoc, they behave exactly like strings with double quotes, except without the double quotes.. thus you don't need to escape those.
It also preserves the line breaks and other whitespace in the text.
The ADMIN_OPTIONS is just a identifier to open and close the operation.
You've got a space after the semicolon in the non-working example, that's why PHP doesn't recognize it.
After viewing the source of the OP one can notice that the spacing and tabulation is not identical in the second case to the first & third cases.
Heredoc like mentioned by many requires that your terminator be the only item on the line. You cannot have a tab, or any other white space preceding it.
Good luck!
PHP's Heredoc examples always seem to use EOT (and sometimes EOD) as the seperating string, while it is actually possible to use any string here. This works:
$mystring = <<<EOT
Foo
Bar
Baz
EOT;
While this works as well:
$mystring = <<<MONKIES
Foo
Bar
Baz
MONKIES;
Does EOT actually stand for something and if so, what?
It stands for "End Of Text".
Actually end of text would be ETX – EOT is end of transmission.
Reference: ASCII - Wikipedia
Short answer
Probably End Of Text and End Of Data.
Long answer
The only ones who can tell you definitively what the acronyms mean are the authors of the original (and current) documentation. But based on an early version of the documentation which mentions "here doc text", I think one could plausibly assume that EOT is intended to mean End of Text.
Similarly, the current documentation makes a comparison between Nowdocs and SGML <![CDATA[ ]]> sections, so a reasonable assumption would be that EOD stands for End Of Data.
Sure, there's a definition of EOT in the ASCII standard, but that refers to a single character 0416 and this definition doesn't transfer to anything else unless explicitly stated. About the only thing we can learn from the ASCII standard in this regard is the encoding of the three letters E, O and T.
This is all guesswork of course, but these are the only sensible explanations I can think of.
Personally, I prefer to avoid the whole issue by using a single underscore (<<<_).
I prefer to go for the TRON reference and use 'EOL' (End of Line).
I'm new to PHP and don't understand what the point of <<<_END is. Could someone please explain when this should be used? I've looked at various examples and they all seem to have HTML embedded within them. But I can use HTML without the <<<_END tags, so why should I use them? I tried searching the manual, but I keep finding the end() method for arrays.
It's the start of a heredoc. you can do:
$data = <<< _END
You can write anything you want in between the start and end
_END;
_END can be just about anything. You could put EOF or STUFF. as long as you use the same thing at the start and the finish.
This signifies the beginning of a heredoc (a multi-line string that allows you to use quotation marks in the middle, unescaped) that ends when you encounter the _END
It can be useful to define HTML in one of these if the goal is to assign it to a variable or pass it to a function rather than printing it to the web server immediately.
That syntax is called heredoc
<<<_END
some text
_END
Basically, it's a way of writing a string without worrying about escaping quotes and so on.
As you've mentioned, it doesn't really provide a lot of benefit over other string formats - although, it does mean you can write a block of HTML without escaping out of PHP with ?>
It also isn't too popular as its use generally goes against the practice of seperating content from logic by embedding the content in the middle of your script.
Does this help? http://www.php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc
It allows you to echo out a block of text (just the same as with echo "words";), but without using the beginning/ending quotes, and without having to escape contained double quotes. Read the manual link above for more detail.
It's a heredoc. It's just a way of defining a string.