Quoting strings: what do YOU do?

[ScallioXTX]

As you all probably know, there are different types of string quoting in PHP.
Let's start with single quote vs double quote:

$bar = "foo";
print "hello $bar"; // prints "hello foo"
print 'hello $bar'; // prints "hello $bar" 

The double quotes replace variables with the value of the variables within the strings, while the single quotes don't.

print "test"; // prints "test"
print 'test'; // also prints "test"
print test; // assuming 'test' is not defined as a constant, also prints "test" 

The result of all three statements is the same, but the interpreter doesn't see it thay way. The last one (print test is definitely the worst, because the compiler will first have to check if 'test' is a defined constant, and only after it figures out this isn't the case, will it print the string "test".
The first example (print "test" also isn't great, because the interpreter has to scan the whole string for occurrences of variables. For this short string this isn't any problem, but for larger strings it might become noticeable.

For these reason I personally ALWAYS stick to single quotes.
What do you use?

[Cups]

That's an interesting question, heres what I found.

When starting out everything was in a print statement.

$name = "Earl"
print("My name is $name");

I mean every single line of HTML. It seemed flawless because it was a discipline I could remember, it was simple and it worked. I rarely come across remaining old code, but sometimes I do, and I groan. Still, not having to debug my print statements left me free to debug everything else I was doing wrong.

Slowly I started to use echo and single concatenated quotes, mostly after reading posts on this subject on this forum.

echo 'My name is ' . $name ;

I found this made my vars easier to spot, and was much influenced by the fact I was learning OOP - which generally speaking, should return data, not echo or print output directly.

I went down the road of comma separated echos for a while:

echo 'My name is ', $name ;

Which is even faster ... wheeee ....

But, I found it harder to be consistent, so I stopped using that.

Then of course Heredoc came out, so monster blocks of code including Javascript (wow!) could finally be injected into your page as is.

So given that I am now layering my applications, generally speaking, not outputting much html directly, I allow myself the freedom to use both single and double quotes as and when the situation suits me. for example a pile of vars to go in a string:

echo "The $size $feline $posture on the $product." ;

( the fat cat sat on the mat )

rather than

echo 'My name is ' . $name ;

Maybe my "readability imperative" is now to do with the flow of data rather than the html.

Choosing single or double quotes is often governed by where its headed, if its back into an Ajax-driven DOM then its often singles inside doubles to minimise all the inevitable backslashing crap.

So when starting out pick one method and stick to it for a while. Train your editor to create the text with a shortcut key.

But when you gain confidence and knowledge, experiment, and don't be afraid to use both/ether.

Eventually this becomes a non-issue as you tend to output very little to the the page, or that output goes into some kind of placeholder, such as a template.

[ScallioXTX]

Thanks for your reply Cups, very nice explanation ! I appreciate it

[AnthonySterling]

I have seem to fallen in love with sprintf as of late, I find it a much cleaner way of concatenating and outputting variables encoded within strings.

Does anyone else do this, or is this just a phase I'm going through?

<?php
$sString = 'foo';
echo $sString;
echo sprintf('Hello %s',$sString);
?>

SilverB.

[Force Flow]

$foo="bar";
echo "My name is ".$foo;

I always use double quotes and always refer to the variable outside the quotes. As far as I know, it's the same basic fail-safe method across PHP, Java, JavaScript, and C#

[ferrari_chris]

$foo="bar";
echo "My name is ".$foo;

I always use double quotes and always refer to the variable outside the quotes. As far as I know, it's the same basic fail-safe method across PHP, Java, JavaScript, and C#

Put me down for one of these please.

I use the same method.

[Stormrider]

$foo="bar";
echo "My name is ".$foo;

I always use double quotes and always refer to the variable outside the quotes. As far as I know, it's the same basic fail-safe method across PHP, Java, JavaScript, and C#

Likewise. I do tend to switch between double and single - I use single for 'simple' text things like constant names in define() etc. Mostly double though, and I never embed variables within it. I don't use heredoc either - I will switch out of PHP instead.

Anyone using efficiency as a reason is doing it wrong! Readability and maintainability is FAR more important than efficiency/speed. The differences are absolutely minute, and you shouldn't code for efficiency except in the most extreme examples, you will end up making your code look awful / nightmare to maintain.

Despite several attempts at trying to work it out, I never ever saw the point of sprintf() or why you should use it.

[logic_earth]

Despite several attempts at trying to work it out, I never ever saw the point of sprintf() or why you should use it.

It is good for ambiguous data into a certain format. For example finding all URLs in a string turning them into html anchors.

<?php

define( 'ANCHOR_FORMAT', '<a href="%s">%s</a>' );

function convertUrls ( $m )
{
    $href = $m[1]; $title = $m[1];
    # Do something with $href and $title
    return sprintf( ANCHOR_FORMAT, $href, $title );
}

$s = preg_replace_callback( '/.../', 'convertUrls', $s );

Using sprintf you can change the format without changing the function. This is of course extremely simplified.

[Jake Arkinstall]

Does anyone else do this, or is this just a phase I'm going through?

Sprintf() was a phase I went though too, but I only stopped because of HereDoc.

HereDoc makes life much, much easier.

echo <<<FORM
    <form action="{$_SERVER['PHP_SELF']}" method="post" onsubmit="alert('I can use both double and single quotes without needing to escape them. Not a care in the world.');" />
        <select name="mySelect">
            {$optionList}
        </select>
        <input type="submit" value="Go go go!" />
FORM; 

[Raju Gautam]

I use Single quotes and of course the variables outside of the quotes but until I go for HeareDoc or NewDoc. Single quotes doesn't take compiler to take care of variable interpolation as far as I know.

[logic_earth]

The only problem with HereDoc is it doesn't look very nice with indented code.

[BrandonK]

$percent = 99.9;
echo 'I use single quotes ' . $percent . '% of the time';

I want to start using Heredoc, but I try not to output large blocks of HTML via php. For large blocks I switch it up a bit and exit out of the parser (this is only for the template layer and never inside of a function):

?>
<form action="<?php echo($form['action']); ?>">
...
</form>
<?php

[ccRicers]

$percent = 99.9;
echo 'I use single quotes ' . $percent . '% of the time';

I want to start using Heredoc, but I try not to output large blocks of HTML via php. For large blocks I switch it up a bit and exit out of the parser (this is only for the template layer and never inside of a function):

?>
<form action="<?php echo($form['action']); ?>">
...
</form>
<?php

I used to escape the PHP code to write large blocks of HTML, but I found it more messy when I started using frameworks. This was the point when I changed the way I integrated PHP into the website.

Now I try to keep the views and logic as separate as possible. All the HTML is on separate php files, and PHP is only present there as presentation logic. (like displaying content through a loop)

[Jake Arkinstall]

The only problem with HereDoc is it doesn't look very nice with indented code.

What do you mean?

[ScallioXTX]

What do you mean?

I think he means this:

<div>
  <div>
    <div>
      <div>
        <?php
           print <<<ENDFORM
           <form method="post" action="$form['action']">
ENDFORM;

Since ENDFORM has to be at the first character of the line, it kinda screws up the "flow" of the page.

[Jake Arkinstall]

The only problem with HereDoc is it doesn't look very nice with indented code.

What do you mean?

[logic_earth]

Simple simple...

<?php

class NothingSpecial
{
    public function nothingHere ()
    {
        $var = <<<EOLINE
...stuff...
    ...stuff...
    ...stuff...
...stuff...
EOLINE;
        return $var;
    }
}

[Jake Arkinstall]

It's just one line that is out if you tab the rest:

<?php

class NothingSpecial
{
    public function nothingHere ()
    {
        $var = <<<EOLINE
            ...stuff...
                ...stuff...
                ...stuff...
            ...stuff...
EOLINE;
        return $var;
    }
}

[logic_earth]

It's just one line that is out if you tab the rest:
<snip>

Only tab the rest if you want those tabs in there. (Not always the case.) Its not really an issue, I just have to look harder while reading the code.

[Cups]

Yeah, same "problem" with vim - it frigs with the code-folding, well, sometimes.

Heredoc states the closing tag must be the first char on a line.

$thing = <<<EOL

Do stuff.

EOL;

In vim, this occasionally causes the code-folder to throw a wobbler, its ok if I close and reopen the file. It doesn't stop me doing using it - its just a PITA.

I had to refactor some stuff this pm, and now I look at it I am amazed how much I have unconciously adopted the method that BrandonK posted about, I just drop in and out of PHP.

Read about the alternative PHP syntax too.

[sk89q]

I usually put my HTML in separate template files. The PHP files are cleaner, easier to read, easier to scan through, easier to modify later, and easier to write.

Although when I do need to use variables in strings, I use whatever is appropriate for the project.

[Cups]

I always use double quotes and always refer to the variable outside the quotes. As far as I know, it's the same basic fail-safe method across PHP, Java, JavaScript, and C#

New information. I might change again now.

Does anyone know offhand how quoting is done in Python? (too busy/lazy to look, atm)

[Jake Arkinstall]

In Python, the basic concatenation operator is +. Both quote types can be used (unlike C# and Java) and also, Print has indefinite params so for speed you could use:

name = 'Rob' + 'ert'
print 'Hello ', name, '!'

It also has a similar way of formatting like PHP's sprintf(), which looks like:

print 'Hello %s!' % (name)

[Cups]

Does anyone know offhand how quoting is done in Python? (too busy/lazy to look, atm)

Thanks Jake.

[stef686]

I prefer single quotes myself, always put my variables outside quotes so singles are faster