What is the best way to add two strings together?

Question

I read somewehere (I thought on codinghorror) that it is bad practice to add strings together as if they are numbers, since like numbers, strings cannot be changed. Thus, ad

Answer 1

For nearly 2 years after last post in this thread, I think that below solution may be the fastest for huge number of tight loops:

ob_start();

echo $str1;
echo $str2;
.
.
.
echo $str_n;

$finalstr = ob_get_clean();

This method ensures a flat storage of all strings and no processing or concatenation overhead. With the final code line, you get entire buffer as well. You can safely run loops instead of independent echos.

Answer 2

This is not a solution for 2 strings, but when you thinking of joining more strings best way like that:

$tmp=srray();
for(;;) $tmp[]='some string';
$str=implode('',$tmp);

It's faster to create array element and join them all at once, than join them hundred times.

Answer 3

String Concatenation with a dot is definitely the fastest one of the three methods. You will always create a new string, whether you like it or not. Most likely the fastest way would be:

$str1 = "Hello";
$str1 .= " World";

Do not put them into double-quotes like $result = "$str1$str2"; as this will generate additional overhead for parsing symbols inside the string.

If you are going to use this just for output with echo, then use the feature of echo that you can pass it multiple parameters, as this will not generate a new string:

$str1 = "Hello";
$str2 = " World";
echo $str1, $str2;

For more information on how PHP treats interpolated strings and string concatenation check out Sarah Goleman's blog.

Answer 4

Unless its really large amount of text it really doesnt matter.

Answer 5

Found this post from Google, and thought I'd run some benchmarks, as I was curious what the result would be. (Benchmarked over 10,000 iterations using a benchmarker that subtracts its own overhead.)

    Which                        2 strings   10 strings   50 strings
    ----------------------------------------------------------------
    $a[] then implode()         2728.20 ps      6.02 μs     22.73 μs
    $a . $a . $a                 496.44 ps      1.48 μs      7.00 μs
    $b .= $a                     421.40 ps ★    1.26 μs      5.56 μs
    ob_start() and echo $a      2278.16 ps      3.08 μs      8.07 μs
    "$a$a$a"                     482.87 ps      1.21 μs ★    4.94 μs ★
    sprintf()                   1543.26 ps      3.21 μs     12.08 μs

So there's not much in it. Probably good to avoid sprintf() and implode() if you need something to be screaming fast, but there's not much difference between all the usual methods.

Answer 6

I'm not a PHP guru, however, in many other languages (e.g. Python), the fastest way to build a long string out of many smaller strings is to append the strings you want to concatenate to a list, and then to join them using a built-in join method. For example:

$result = array();
array_push("Hello,");
array_push("my");
array_push("name");
array_push("is");
array_push("John");
array_push("Doe.");
$my_string = join(" ", $result);

If you are building a huge string in a tight loop, the fastest way to do it is by appending to the array and then joining the array at the end.

Note: This entire discussion hinges on the performance of an array_push. You need to be appending your strings to a list in order for this to be effective on very large strings. Because of my limited exposure to php, I'm not sure if such a structure is available or whether php's array is fast at appending new elements.