Performance of inequality operator

Question

It appears that (!$a == 'hello') is consistently faster than ($a != 'hello')

// (!$a == 'hello')
Used time: 52.743232011795
Used time: 52.633831977844
Used time: 51.452646970749

//($a != 'hello')
Used time: 76.290767908096
Used time: 81.887389183044
Used time: 64.569777011871

Any idea why this is happening? I understand that this level of optimization is irrelavent in most of the cases. The question is purely out of curiosity. (Ref: http://www.php.net/manual/en/language.operators.comparison.php#99216)

Those two operations do not have the same result. – deceze Jan 21 '12 at 01:03 — deceze, Jan 21 '12 at 01:03
@milo Yes. It's the same code in the PHP reference above. – mixdev Jan 21 '12 at 01:09 — mixdev, Jan 21 '12 at 01:09
@mixdev Sorry, I missed the link to the code. – Milo LaMar Jan 21 '12 at 01:34 — Milo LaMar, Jan 21 '12 at 01:34

score 5 · Accepted Answer · answered Jan 21 '12 at 01:07

5

!$a == 'hello' casts $a to a (negated) boolean and compares that to a string. That may be faster, since it's easier to decide than actually comparing two strings. It'll also give you wrong results. What you need to compare against is !($a == 'hello'), which I would guess is about equal in time taken.

answered Jan 21 '12 at 01:07

deceze

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You are correct. I tested it and !($a == 'hello') is comparable in performance. – mixdev Jan 21 '12 at 01:25

Performance of inequality operator

1 Answers1