PHP - concatenate or directly insert variables in string

I am wondering, What is the proper way for i开发者_如何学Gonserting PHP variables into a string?

This way:

echo "Welcome ".$name."!"

Or this way:

echo "Welcome $name!"

Both of these methods work in my PHP v5.3.5. The latter is shorter and simpler but I'm not sure if the first is better formatting or accepted as more proper.

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Between those two syntaxes, you should really choose the one you prefer :-)

Personally, I would go with your second solution in such a case (Variable interpolation), which I find easier to both write and read.

The result will be the same; and even if there are performance implications, those won't matter ¹.

As a sidenote, so my answer is a bit more complete: the day you'll want to do something like this:

echo "Welcome $names!";

PHP will interpret your code as if you were trying to use the $names variable -- which doesn't exist. - note that it will only work if you use "" not '' for your string.

That day, you'll need to use {}:

echo "Welcome {$name}s!"

No need to fallback to concatenations.

Also note that your first syntax:

echo "Welcome ".$name."!";

Could probably be optimized, avoiding concatenations, using:

echo "Welcome ", $name, "!";

(But, as I said earlier, this doesn't matter much...)

_{1 - Unless you are doing hundreds of thousands of concatenations vs interpolations -- and it's probably not quite the case.}

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Double-quoted strings are more elegant because you don't have to break up your string every time you need to insert a variable (like you must do with single-quoted strings).

However, if you need to insert the return value of a function, this cannot be inserted into a double-quoted string--even if you surround it with braces!

//syntax error!!
//$s = "Hello {trim($world)}!"

//the only option
$s = "Hello " . trim($world) . "!";

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Since php4 you can use a string formater:

$num = 5;
$word = 'banana';
$format = 'can you say %d times the word %s';
echo sprintf($format, $num, $word);

Source: sprintf()

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I prefer this all the time and found it much easier.

echo "Welcome {$name}!"

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From the point of view of making thinks simple, readable, consistent and easy to understand (since performance doesn't matter here):

• Using embedded vars in double quotes can lead to complex and confusing situations when you want to embed object properties, multidimentional arrays etc. That is, generally when reading embedded vars, you cannot be instantly 100% sure of the final behavior of what you are reading.

• You frequently need add crutches such as {} and \, which IMO adds confusion and makes concatenation readability nearly equivalent, if not better.

• As soon as you need to wrap a function call around the var, for example htmlspecialchars($var), you have to switch to concatenation.

• AFAIK, you cannot embed constants.

In some specific cases, "double quotes with vars embedding" can be useful, but generally speaking, I would go for concatenation (using single or double quotes when convenient)

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I know this question already has a chosen answer, but I found this article that evidently shows that string interpolation works faster than concatenation. It might be helpful for those who are still in doubt.

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Either one is fine. Use the one that has better visibility for you. And speaking of visibility you can also check out printf.

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I use a dot(.) to concate string and variable. like this-

echo "Hello ".$var;

Sometimes, I use curly braces to concate string and variable that looks like this-

echo "Hello {$var}";

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Do not concatenate. It's not needed, us commas as echo can take multiple parameters

echo "Welcome ", $name, "!";

Regarding using single or double quotes the difference is negligible, you can do tests with large numbers of strings to test for yourself.

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Go with the first and use single quotes!

1. It's easier to read, meaning other programmers will know what's happening
2. It works slightly faster, the way opcodes are created when PHP dissects your source code, it's basically gonna do that anyway, so give it a helping hand!
3. If you also use single quotes instead of double quotes you'll boost your performance even more.

The only situations when you should use double quotes, is when you need \r, \n, \t! The overhead is just not worth it to use it in any other case.

You should also check PHP variable concatenation, phpbench.com for some benchmarks on different methods of doing things.

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It only matter of taste.
Use whatever you wish.

Most of time I am using second one but it depends.

Let me suggest you also to get yourself a good editor which will highlight a variable inside of a string

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You Should choose the first one. They have no difference except the performance the first one will be the fast in the comparison of second one.

If the variable inside the double quote PHP take time to parse variable.

Check out this Single quotes or double quotes for variable concatenation?

This is another example Is there a performance benefit single quote vs double quote in php?

I did not understand why this answer in above link get upvoted and why this answer got downvote.

As I said same thing.

You can look at here as well

What is faster in PHP, single or double quotes?

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I know this is an old question, but I think someone has to mention all pros & cons:

Better Syntax: That's personal preference.

Performance: No difference. As many mentioned, double-quote might be faster if using unrealistically many variables.

Better Usage: Single quote (mostly). As @Khez said, with single quote you can concatenate anything, even function calls and variable modification, like so: echo 'hi ' . trim($name) . ($i + 1);. The only thing double-quote can do that single-quote cannot do is usage of \n, \r, \t and alike.

Readability: No difference (may personal preference apply).

Writability/Re-Writability/Debugging: In 1-line statements there is no difference, but when dealing with multiple lines, it's easier to comment/uncomment lines while debugging or writing. For example:

$q = 'SELECT ' .
     't1.col1 ' .
     ',t2.col2 ' .
   //',t3.col3 ' .
     'FROM tbl1 AS t1 ' .
     'LEFT JOIN tbl2 AS t2 ON t2.col2 = t1.col1 ' .
   //'LEFT JOIN tbl3 AS t3 ON t3.col3 = t2.col2 ' .
     'WHERE t1.col1 = ' . $x . ' ' .
     '  AND t2.col2 = ' . $y . ' ' .
   //'  AND t3.col3 = ' . $z . ' ' .
     'ORDER BY t1.col1 ASC ' .
     'LIMIT 10';

Less Escaping: Single-quote. For single quote you need to escape 2 characters only (' and \). For double quote you need to escape 2 characters (", \) and 3 more if required ($, { and }).

Less Changes: Single quote. For example if you have the following code:

echo 'Number ' . $i . '!';

And you need to increment 1 to $i, so it becomes likes:

echo 'Number ' . ($i + 1) . '!';

But for double quote, you will need to change this:

echo "Number $i!";

to this:

echo "Number " . ($i + 1) . "!";

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Conclusion: Use what you prefer.

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If you want to execute a SQL command and your variables are array members, then you should not use single quotes inside [] of array (like this: ['']); for example if you use this string as a SQL command, you get server error 500:

$con = mysqli_connect('ServerName', 'dbUsername', 'dbPassword');
mysqli_select_db($con, 'dbName')

//'ID' is auto increment field.
$sql = "INSERT INTO sampleTable (ID, TraceNo) VALUES ('','$sampleArray['TraceNo']')";
mysqli_query($con, $sql)

The correct string is:

//'ID' is auto increment field.
$sql = "INSERT INTO sampleTable (ID, TraceNo) VALUES ('','$sampleArray[TraceNo]')";

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echo "Welcome $name!";

This is the best way.

You don't need to anything else