Logische Operatoren
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);
?>
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
Zeichenketten-Operatoren - [5 notes]
anders dot benke at telia dot com ¶
9 years ago
K.Alex ¶
4 months 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 $arty, which is undefined
?>
hexidecimalgadget at hotmail dot com ¶
4 years ago
If you attempt to add numbers with a concatenation operator, your result will be the result of those numbers as strings.
<?php
echo "thr"."ee"; //prints the string "three"
echo "twe" . "lve"; //prints the string "twelve"
echo 1 . 2; //prints the string "12"
echo 1.2; //prints the number 1.2
echo 1+2; //prints the number 3
?>
Stephen Clay ¶
7 years ago
<?php
"{$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.
mariusads::at::helpedia.com ¶
4 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.