PHP short circuit lazy evaluation, where is it in the php.net manual?

Question

Sorry if this sounds like a really silly question.

But I Googled the web and also Googled specifically both the php.net site and the stackoverflow.com site. I know PHP does short circuit lazy evaluation when using and, or, &&, || operators, but where is it stated loud and clear in the PHP manual???

I found only Wikipedia as the only 'trusted' source that say PHP does lazy evaluation on these operators.

I don't know where it's written either, but it's taken for granted a good number of times, for instance when people call like mysql_connect(...) || die("Connection failed");. — zneak
– zneak, Commented Jul 10, 2010 at 21:38
The most trustworthy source is the source code itself. And as far as I remember from the last time I read it, it's true. — Ionuț G. Stan
– Ionuț G. Stan, Commented Jul 10, 2010 at 21:39
Does it matter that it's said to be official or not? It's the way PHP works, code with that idea in mind. — Matt S
– Matt S, Commented Jul 10, 2010 at 21:42
Hugh, my question wasn't that silly since someone placed a +1 vote. — Marco Demaio
– Marco Demaio, Commented Jul 10, 2010 at 21:55
+1: It's a very reasonable concern. It's certainly possible to program without a clear spec, relying on inferences from code examples, hearsay about the intentions of the designers, and poking around the details of the current implementation. But anyone who has to work like that is entitled to worry that their house is built on sand. — user8599
– user8599, Commented Aug 19, 2011 at 1:58

Mike B · Accepted Answer · 2010-07-10 21:37:58Z

9

Closest thing I can find to an 'official' mention of PHP's short-circuit implementation: http://php.net/manual/en/language.operators.logical.php

answered Jul 10, 2010 at 21:37

Mike B

32.2k13 gold badges90 silver badges113 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

zneak Over a year ago

It's written inside the code snippet. First comment: // foo() will never get called as those operators are short-circuit

Marco Demaio Over a year ago

Thanks for the help!!! It's not stated loud and clear, but it's written there and also with clear examples.

Pang Over a year ago

How about short-circuiting for ?:? Come on, PHP, look at Java.

Paul Dixon · Accepted Answer · 2010-07-10 21:40:36Z

1

This is not an uncommon feature of expression evaluation. The PHP manual page on logical operators makes a passing reference to it in one of the illustrative examples though.

Short circuit evaluation is a commonly exploited idiom, and you can rely on its continued support in the language, otherwise vast amounts of code would break!

answered Jul 10, 2010 at 21:40

Paul Dixon

302k54 gold badges315 silver badges349 bronze badges

Collectives™ on Stack Overflow

PHP short circuit lazy evaluation, where is it in the php.net manual?

2 Answers 2

3 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related