once & for all: 'single' quotes or "double" quotes? what's official / better / right?

marcnyc

Hi, I have been wondering about this ever since I looked at a PHP page for the first time and now I am facing the issue myself, so I hope some heavy-weight PHP person here can clarify my ideas once and for all...

Is there a standard convention in PHP or even in HTML about the use of single quotes or double quotes?

For example, is it:
echo "hi";
or
echo 'hi';
???

...is it:
<input type="text" name="var">
or
<input type='text' name='var'>
???

I have even seen:
<input type=text name=var>
is this possible/correct at all????

For example these days I am working on something where I have PHP echo-ing forms, so I am using:
echo '<input type="text" name="var">';
echo '<input type=\'text\' name=\'var\'>';
echo "<input type=\"text\" name=\"var\">";
echo "<input type='text' name='var'>";

Which one is better among these (if any)???

Also I am running into serious complications while working on this project where I create files on the server with fopen() and I end up with complicated strings like these:

$string .= "\n	echo \"<input type='text' name='var'></form>\"; \r";

So far so good... but in many cases the variable var will contain single quotes and double quotes and I am literally LOOSING MY MIND with multiple, nested str_replace to make sure the output does not interfere with the three levels of quotes... I am going crazy, so if you have advices or standard rules to share with me, I'd gladly learn the right way once and for all!

SpasePeepole

It doesn't really matter. If you use " and you need a " in the string, you will have to escape it with . And if you have ', you will have to escape ' with . I personally prefer Single Quotes when using php to echo HTML text so I don't have to escape all of the quotes

Weedpacket

Originally posted by marcnyc
Is there a standard convention in PHP or even in HTML about the use of single quotes or double quotes?

The only difference in PHP is as Spacepeeple describes, with the exception in PHP that variables are interpolated in double-quoted strings but not in single-quoted ones. One other place where your choice makes a difference is if you're using the htmlspecialchars() function, since that needs to know if the string it returns will be going into an HTML attribute value that is single- or double-quoted.

For example, is it:
echo "hi";
or
echo 'hi';
???

Whichever takes your fancy.

...is it:
<input type="text" name="var">
or
<input type='text' name='var'>
???

Either one, but for convenience, use the one opposite to your PHP convention (to avoid all those quoting hassles).

I have even seen:
<input type=text name=var>
is this possible/correct at all????

This is bad/nonstandard. Do not do it. It only gets you into trouble later (<input type=text name=var value=some text> - broken).

A couple of other suggestions. If you're just outputting plain HTML, without doing any processing on it, don't bother doing it in PHP at all:

$some=PHP();
?>

<input type="text" name="thingy">
<?php //Back into PHP

That saves you one level of quotes. It's nice in forms, because you can just the occasional <?php echo $variable?> any time you need to.

Another saving is to use the heredoc syntax:

$string .= <<<EOF

echo "<input type='text' name='var'></form>";\r

EOF;
[/b]

which also saves you a level of quotes - it's especially good for big blocks of text that need to go into variables (instead of being output):

$capitalised_text = 'LOSING MY MIND';
$a_quoted_paragraph = <<<EOP
So far so good... but in many cases the variable var will contain single quotes and double quotes and I am literally $capitalised_text with multiple, nested str_replace to make sure the output does not interfere with the three levels of quotes... I am going crazy, so if you have advices or standard rules to share with me, I'd gladly learn the right way once and for all!
EOP;

With those provisos, the decision of which method to use in a given situation is a matter of style and readability.

devinemke

single quotes should be used whenever possible so that the PHP parser does not have to do needless checking for varibale expansion:

<?
$name = 'Joe Smith';
echo 'My name is ' . $name;
?>

will run slightly faster than:

<?
$name = 'Joe Smith';
echo "My name is $name";
?>

obviously this is a simplified example and the speed difference is negligible but i think is is a good habit to use single quotes and concatenate varibales, in a large script with thousands of lines of code the speed difference could become more of a factor.

ahundiak

With respect to html, the choice between using single or double quotes for attribute values is pretty easy. Always use double quotes. Html itself is pretty much frozen and is slowly being replaced by xhtml which requires the use of double quotes. All other things being equal, you may as well code against the most up to date standard.

There are some other differences between html and xhtml.

http://www.w3.org/TR/2002/REC-xhtml1-20020801/#diffs

Kerry_Kobashi

Always use double quotes in HTML tags and make it a habit.
This is strongly recommended in XHTML 1.x...

Kerry Kobashi
Kobashi Computing

marcnyc

Wow, I expected this to quickly become an animated discussion, and WOW Weedpacket, you are following me every where englightening me with your great knowledge. I deeply appreciate that... I might have to start paying you a salary as my personal advisor ;-) I also love (and thank you for) replying to all my points, quoting one after the other... I will make sure to credit all of you in my project and you first of all!!!

This is bad/nonstandard. Do not do it. It only gets you into trouble later (<input type=text name=var value=some text> - broken).

Yes, I had figured that myself some time ago... in fact I never use it, but I was just curious!

Another saving is to use the heredoc syntax:

$string .= <<<EOF
echo "<input type='text' name='var'></form>";\r
EOF;
[/b]

Wow, you got my attention with this one! I was unaware of this method (I am still learning, ladies and gentlemen) but if I understood you correctly this will save my light and bring my code down from 10 pounds to 1 pound!

So do you mean I can do that with every $string. ==; type when using fopen()? or are there any counter-effects I should know about before converting all my big code and removing all the now useless str_replace???

which also saves you a level of quotes - it's especially good for big blocks of text that need to go into variables (instead of being output):

And that is exactly my case, since I am building an automatic interview system all my variables (the answers and the questions) will have BIG text and lots of characters (single quotes, double quotes, slashes, backslashes etc etc) in it...

Thanks a lot!!!!!!!!!

Weedpacket

Originally posted by marcnyc
So do you mean I can do that with every $string. ==; type when using fopen()? or are there any counter-effects I should know about before converting all my big code and removing all the now useless str_replace???

Well, I'm not sure what you're meaning here, but as a quoting style, there are only two or three things (maybe four) to note about it:

$string = <<<EOF
This is a big block of text, all sorts of stuff appears in it. It's literal text, the same as you get in '- or "=quoted strings, so function calls can't be used (because PHP has no way of telling if fopen('somefile.txt') is a function or just more text - so if you want to stick in the result of a function, put it in a variable first; variables are interpolated. String concatentation may or may not work (something to try) as noted in the next paragraph. The resulting string variable will contain a bog-standard string the same as if it had been quoted some other way.

The closing delimiter (EOF in this case), has to be the first thing in it's line - no indenting. And, apart from the (possible?) semicolon, the only thing. Further, it's best if the opening delimiter is the last thing on its line. The newline characters at the very beginning and end of this block of text (immediately after the opening delimiter and immediately before the closing one) are ignored. If you want to concatenate another string to this one, the '.' operator would have to be on the next line after the closing delimiter (you wouldn't have a semicolon, either, of course); but note that never having tried it, I'm not entirely certain if that would work.

The choice of delimiter is pretty free; EOF is traditional, and short strings of ALLCAPS are conventional, but the most important thing is that none of lines of text in the string starts with the delimiter in the first column.

Many syntax-highlighting editors have trouble with it...
EOF;

Weedpacket

Originally posted by ahundiak
With respect to html, the choice between using single or double quotes for attribute values is pretty easy. Always use double quotes. Html itself is pretty much frozen and is slowly being replaced by xhtml which requires the use of double quotes. All other things being equal, you may as well code against the most up to date standard.

My reading of the XML standard is that either single or double quotes may be used (this is specified explicitly in its definition of attribute-value pairs) and doesn't express a preference one way or the other. (XHTML doesn't change this, as doing so would violate the XML standard it's supposed to be built on.) The W3C happens to use double-quotes by convention, and I happen to use double-quotes by convention, too, but that's only a convention I use for the sake of being consistent and not causing problems for myself later.

marcnyc

So, let me see if I understand correctly...

Can I change this:

$string = "
\n echo '<input type="hidden" name="var" value=".$phpvar.">';
\r";
$string .= "
\n echo '<input type="submit" name="Submit" value="Ok"></form>';
\r";

into this:

$string = <<<EOF 
\n echo '<input type="hidden" name="var" value="
EOF;.$phpvar.<<<EOF >';
\r
EOF;
$string .= <<<EOF 
\n echo '<input type="submit" name="Submit" value="Ok"></form>';
\r
EOF;

????????????

or is it wrong?

EDITED: For some reason this forum stripped the slashes from my \n and \r only in the second example I did but of course what I am concerned about is how to temporarily escape the <<<EOF EOF; thing to print an array's values... you know, how you would ".$array[$i]."

Weedpacket

Not quite. In heredoc-quoted strings (and multi-line '- or "-quoted strings), newline characters really are newline characters,
like
this,
instead of escapes.

And I'm not sure the \r would be necessary (even on Windows machines, unless perhaps you were wanting to later open it in a text-editor that wasn't smart enough to recognise Unix-style newlines).

$string = <<<EOF

echo '<input type="hidden" name="var" value="$phpvar">';

EOF;

$string .= <<<EOF

echo '<input type="submit" name="Submit" value="Ok"></form>';

EOF;

Or, if you're going to be like that:

$string = <<<EOF

echo '<input type="hidden" name="var" value="$phpvar">';
echo '<input type="submit" name="Submit" value="Ok"></form>';

EOF;

And see point 4 about the colour scheme 🙂

marcnyc

I am slightly confused here...

I understand I don't need to use newlines and \r because new lines are created if I put them inside the EOF tags, but what I don't understand is how to get the value of the variable or array $phpvar inside the php code that will be the code of my newly fopen()-created file...

I mean, I have page1.php with this code:

$phpvar = "test";

fopen() //and all the other necessary code to create the file

$string = <<<EOF
echo '<input type="hidden" name="var" value="$phpvar">';
echo '<input type="submit" name="Submit" value="Ok"></form>';
EOF;

etc etc...

basically my question is: will the instance of $phpvar between EOF tags be converted in the word test so that the newly created file will contain this code:

echo '<input type="hidden" name="var" value="test">';
echo '<input type="submit" name="Submit" value="Ok"></form>';

?????

marcnyc

Sorry, but is it EOF or EOP? I just realized that EOF didn't work in a test I made and when I went back to your post I realized you posted EOF once and EOP another time...

I made a test:

$phpvar = "test"; 

$string = <<<EOP
this 'is' a "$phpvar" and I love it
EOP;

echo $string;

It worked. The output was:
this 'is' a "test" and I love it

But then I run another test which was:

$phpvar = "test"; 

$string = <<<EOP
this 'is' a "
EOP;
echo $phpvar;
$string .= <<<EOP
" and I love it
EOP;

echo $string;

and the result wasn't quite perfect as it printed:
testthis 'is' a "" and I love it

I would love to use the first of the two methods but I need to be able to apply str_replace() and stripslashes() etc to my variables and arrays INSIDE the EOF/P...

I would like to be able to do this:

$string = <<<EOP
this 'is' a ".stripslashes($phpvar)." and I love it
EOP;

or at least this:

$string = <<<EOP
this 'is' a "EOP;stripslashes($phpvar)<<<EOP
" and I love it
EOP;

but of course they both don't work... is there a way around it besides applying the functions on the variable in the line before the variable is put into the EOP string?

Also the value of the $phpvar or array be printed inside the EOP so that if I am creating a new file on disk with fopen() and the $string lines are the lines of the new file, this new file will actually contain the value of the variable and not the variable itself (which would of course not have a value assigned to it)?

Weedpacket

Originally posted by marcnyc
Sorry, but is it EOF or EOP? I just realized that EOF didn't work in a test I made and when I went back to your post I realized you posted EOF once and EOP another time...

See point three. EOF should work; EOP works too, ALLCAPS would be fine. (If you're writing code that writes code (Unix shell scripting is a prime example) it's sometimes necessary to quote a heredoc-quoted string inside a heredoc-quoted string. Just use different delimiters for the inner and outer strings.) I just used EOP in one place to point out that you don't have to use EOF; EOF is kind of a geek pun ("End Of File"). I just used EOP for "End Of Paragraph", 'cos that's what it was delimiting. EOT or EOS are also commonly used. Whatever you're comfortable with, so long as the opening and closing delimiters match.

If EOF didn't work - are you sure it there was nothing else on the line? No indentation, no trailing whitespace?

But then I run another test which was:
$phpvar = "test"; 

$string = <<<EOP
this 'is' a "
EOP;
echo $phpvar;
$string .= <<<EOP
" and I love it
EOP;

echo $string;
and the result wasn't quite perfect as it printed:
testthis 'is' a "" and I love it

That's to be expected:

Set $phpvar to the value test;
Set $string to the value this 'is' a ";
Echo the value of $phpvar;
Concatenate " and I love it onto $string.
Echo $string.

In short that third line should be $string .= $phpvar;

I would love to use the first of the two methods but I need to be able to apply str_replace() and stripslashes() etc to my variables and arrays INSIDE the EOF/P...

Not inside the heredoc-quoted text itself, sorry (that was point 2). But then you can't do that in '- or "-quoted strings either:

$phpvar="stripslashed";
$string="This is some stripslashes($phpvar) text.";

wouldn't work.

$string = <<<FOO
this 'is' a "
FOO;
$string.=stripslashes($phpvar);
$string .= <<<BAR
" and I love it
BAR;

...and I changed the delimiters just 'cos I CAN.

matto

as for the double versus single quote question, about 1 1/2 years ago I read an interesting argument in this forum:

because magic-quoted strings are "parsed", the processing takes a bit longer.

therefore, when I have to output lots of text (e.g. in loops), I now use magic quotes only if necessary/reasonable.

however I never noticed a real performance issue due to the parsing.

in doubt, I would use magic quotes. the interpolation of variables is one of the many nice features of php which made it so comfortable to learn and use - and thus popular.

marcnyc

Originally posted by Weedpacket
In short that third line should be $string .= $phpvar;

Ok, that helps!

$string="This is some stripslashes($phpvar) text.";
wouldn't work.

Yes, that wouldn't work, but:
$string="This is some ".stripslashes($phpvar)." text.";
would work, and that is what I was doing...

...and I changed the delimiters just 'cos I CAN.

Foo Bar? Allright so that means I can use <<<MARC MARC; ? ;-)

BTW, what are the magic quotes Matto is talking about? Is that another name for single quotes?

Weedpacket

The magic quotes would be the double ones, 'cos they do variable interpolation.

echo <<<BLARNEY
I've found that it doesn't make much difference which you use until you actually do have variables in the string (it takes much longer to actually do variable interpolation than it does to find out if there are any variables to interpolate!)
BLARNEY;

But then, if you want to do variable interpolation, you wouldn't be uising single quotes 🙂. Oh, and ecapes like \n, \r, \t aren't converted in single-quoted strings either.

GUY

Check this out

http://lists.w3.org/Archives/Public/www-html-editor/2001AprJun/0473.html