PHP 5.4.31 Released

Zeichenketten-Operatoren

Es gibt in PHP zwei Operatoren für string (Zeichenkette). Der erste ist der Vereinigungs-Operator ('.'), dessen Rückgabewert eine zusammengesetzte Zeichenkette aus dem rechten und dem linken Argument ist. Der zweite ist der Vereinigungs-Zuweisungsoperator ('.='), der das Argument auf der rechten Seite an das Argument der linken Seite anhängt. Siehe Zuweisungs-Operatoren für weitere Informationen.

<?php
$a 
"Hallo ";
$b $a "Welt!"// $b enthält jetzt den Text "Hallo Welt!"

$a "Hallo ";
$a .= "Welt!";    // $a enthält jetzt den Text "Hallo Welt!"
?>

Siehe auch die Abschnitte über Strings / Zeichenketten und String-Funktionen.

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User Contributed Notes 10 notes

up
33
hexidecimalgadget at hotmail dot com
5 years ago
If you attempt to add numbers with a concatenation operator, your result will be the result of those numbers as strings.

<?php

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

?>
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25
K.Alex
1 year 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:

<?php

$a
= '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

?>
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18
anders dot benke at telia dot com
10 years ago
A word of caution - the dot operator has the same precedence as + and -, which can yield unexpected results.

Example:

<php
$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:

<php
$var = 3;

echo "Result: " . ($var + 3);
?>
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12
mariusads::at::helpedia.com
5 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.
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13
Stephen Clay
8 years ago
<?php
"{$str1}{$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.
up
1
patel405nishant at gmail dot com
3 months 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:

<?php

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

echo
"$var" . '$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.
up
-16
mostafa dot ali106 at gmail dot com
7 months 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:

<?php

$var
= "hello";

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

?>

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.
up
-18
mostafa dot ali106 at gmail dot com
7 months 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:

<?php

$var
= "hello";

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

?>

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.
up
-23
mostafa dot ali106 at gmail dot com
7 months 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:

<?php

$var
= "hello";

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

?>

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.
up
-30
mostafa dot ali106 at gmail dot com
7 months 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:

<?php

$var
= "hello";

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

?>

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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