September 2009
Intermediate to advanced
912 pages
48h 11m
German
book
PHP 5 Kochbuch, Third Edition
by David Sklar, Adam Trachtenberg, Carsten Lucke, Matthias Brusdeylins, Ulrich Speidel, Stephan Schmidt
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5.2 Einen Vorgabewert festlegen
Problem
Sie möchten einer Variablen einen Vorgabewert zuweisen, sofern diese nicht schon einen Wert hat. Es kommt häufig vor, dass Sie einen fest programmierten Wert für eine Variable verwenden, der durch eine Formulareingabe oder eine Umgebungsvariable überschrieben werden kann.
Lösung
Verwenden Sie isset(), um einer Variablen einen Vorgabewert zuzuweisen, die möglicherweise schon einen Wert hat:
if (! isset($autos)) { $autos = $vorgabe_autos; }Verwenden Sie den ternären Operator (a ? b : c), um einer neuen Variablen einen Wert (gegebenenfalls die Vorgabe) zu geben:
$autos = isset($_REQUEST['autos']) ? $_REQUEST['autos'] : $vorgabe_autos;
Diskussion
Sie müssen vor der Zuweisung von Vorgabewerten isset() aufrufen, da andernfalls ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.