PHP 7.0.6 Released


文字列の演算子は 2 種類あります。最初のは結合演算子('.')で、右引数と 左引数を結合したものを返します。2 番目は、結合代入演算子('.=')で、 この演算子は右側の引数に左側の引数を追加します。詳細は、代入演算子 を 参照ください。

"Hello ";
$b $a "World!"// $b は、"Hello World!" となります。

$a "Hello ";
$a .= "World!"// $a は、"Hello World!" となります。

文字列文字列 関数も参照してください。

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User Contributed Notes 6 notes

anders dot benke at telia dot com
12 years ago
A word of caution - the dot operator has the same precedence as + and -, which can yield unexpected results.


$var = 3;

echo "Result: " . $var + 3;

The above will print out "3" instead of "Result: 6", since first the string "Result3" is created and this is then added to 3 yielding 3, non-empty non-numeric strings being converted to 0.

To print "Result: 6", use parantheses to alter precedence:

$var = 3;

echo "Result: " . ($var + 3);
Stephen Clay
10 years ago
"{$str1}{$str2}{$str3}"; // one concat = fast
$str1. $str2. $str3;   // two concats = slow
Use double quotes to concat more than two strings instead of multiple '.' operators.  PHP is forced to re-concatenate with every '.' operator.
3 years ago
As for me, curly braces serve good substitution for concatenation, and they are quicker to type and code looks cleaner. Remember to use double quotes (" ") as their content is parced by php, because in single quotes (' ') you'll get litaral name of variable provided:


= '12345';

// This works:
echo "qwe{$a}rty"; // qwe12345rty, using braces
echo "qwe" . $a . "rty"; // qwe12345rty, concatenation used

// Does not work:
echo 'qwe{$a}rty'; // qwe{$a}rty, single quotes are not parsed
echo "qwe$arty"; // qwe, because $a became $arty, which is undefined

hexidecimalgadget at hotmail dot com
7 years ago
If you attempt to add numbers with a concatenation operator, your result will be the result of those numbers as strings.


echo "thr"."ee";           //prints the string "three"
echo "twe" . "lve";        //prints the string "twelve"
echo 1 . 2;                //prints the string "12"
echo 1.2;                  //prints the number 1.2
echo 1+2;                  //prints the number 3

7 years ago
Be careful so that you don't type "." instead of ";" at the end of a line.

It took me more than 30 minutes to debug a long script because of something like this:

echo 'a'.
$c = 'x';
echo 'b';
echo 'c';

The output is "axbc", because of the dot on the first line.
patel405nishant at gmail dot com
2 years ago
Please note that PHP does not differentiate between double quotes and single quotes when it comes to concatenating.

Meaning that you can use this:


= "hello";
$world = "world";

"$var" . '$world'; //outputs hello$world

echo "$var" . "$world"; //outputs helloworld

echo "$var" $world; //outputs helloworld


so you can use both at the same time, you can use it to evaluate a portion of the string and keep other parts unevaluated.
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