June 2005
Intermediate to advanced
794 pages
18h 27m
German
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5.1 Die Verwechslung von == und = vermeiden
Problem
Sie möchten beim Vergleich von Variablen mit Konstanten nicht versehentlich Werte zuweisen.
Lösung
Schreiben Sie:
if (12 == $zwerge) { ... }an Stelle von:
if ($zwerge == 12) { ... }Die Konstante auf der linken Seite löst einen Parser-Fehler aus, wenn sie mit dem Zuweisungsoperator verwendet wird. Mit anderen Worten: PHP beschwert sich, wenn Sie schreiben:
if (12 = $zwerge) { ... }führt aber:
if ($zwerge = 12) { ... }stillschweigend aus; dabei wird der Variablen $zwerge der Wert 12 zugewiesen und anschließend der Code im Block ausgeführt ($zwerge = 12 ergibt 12, und das ist true.)
Diskussion
Wenn Sie die Konstante auf der linken Seite des Vergleichs eintragen, erfolgt der Vergleich mit dem Typ der Konstanten. ...
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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.