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Posted by Shelly on 09/24/07 20:40
"Steve" <no.one@example.com> wrote in message
news:r6VJi.36$Nr6.32@newsfe05.lga...
>
> "Joe" <joe@faceh.com> wrote in message
> news:1190663828.772978.15800@22g2000hsm.googlegroups.com...
>>I am just starting to use Object Oriented PHP coding, and I am seeing
>> quite often the following (this example taken from a wiki):
>>
>> $wakka =& new Wakka($wakkaConfig);
>>
>> What exactly is the =&, and why is it different from = ?
>
> well, better syntax would have helped. it should read ' $something =
> &$variable'. in this context, & means 'a reference to the memory location
> where the value is stored'. without the &, it means 'a copy of the value
> of the variable'.
>
> clear as mud? rather than explain memory, let me have you do this:
>
> $variable = 'hello';
> $reference = &$variable;
> $variable = 'world';
> echo '<pre>' . print_r($reference, true) . '</pre>';
> $reference = 'good-bye';
> echo '<pre>' . print_r($variable, true) . '</pre>';
>
> unset($variable);
> unset($reference);
>
> $variable = 'hello';
> $reference = $variable;
> $variable = 'world';
> echo '<pre>' . print_r($reference, true) . '</pre>';
> $reference = 'good-bye';
> echo '<pre>' . print_r($variable, true) . '</pre>';
>
> the first example, BY REFERENCE, means that both $variable and $reference
> point to the same memory location. changing one but using the other makes
> no difference - using either will have the same effect.
>
> the second, BY VALUE, means that each variable points to two different
> locations in memory. the only time they will be equal is when setting them
> so. once you modify one of them, you have done so idependently of the
> other - changing one has no effect on the other.
>
> hope that makes more sense.
That was probably the single most unique new concept (pointers and
address-of) I had conquer when (os so many years ago) I learned C, coming
from a Fortran background as I did.
Shelly
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