dreamcatcher
msg:3912374 | 6:15 am on May 13, 2009 (gmt 0) |
Hi acemaster, Its called 'Passing by Reference'. It means that both your variables point to the same content. This should help you out: [uk.php.net...] dc
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acemaster
msg:3912436 | 8:54 am on May 13, 2009 (gmt 0) |
Thanks dc, but it doesn't say anywhere about being able to use it as a comparison operator, at least I couldn't find it.
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enigma1
msg:3912443 | 9:37 am on May 13, 2009 (gmt 0) |
It's not a comparison operator, you are using it as a logical "AND" operator in your code. So if you take this part alone of the if statement $b &= $c is basically $b = $b&$c (logical and assignment)
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penders
msg:3912450 | 9:50 am on May 13, 2009 (gmt 0) |
Yes, as enigma1 states. Not to be confused with the similar looking 'assign/pass' by Reference (=&) &= ... Logical bitwise AND
=& ... 'assign' by Reference
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penders
msg:3912453 | 10:11 am on May 13, 2009 (gmt 0) |
Just as a matter of interest, have you tried echo'ing the values of $a, $b, $c and $d after your if() statement (if the values are initially different and not equal)? Something like: $a = "test1";
$b = "test2";
$c = "test3";
$d = "test4";
if ($a == $b &= $c &= $d) {
echo "true";
}else{
echo "false";
}
echo '<br>';
echo "$a - $b - $c - $d"; |
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Results in:
false
test1 - test0 - test0 - test4 |
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Which is not what you require. (Bitwise Operators [php.net]) Just expanding on what enigma1 wrote above... The bitwise assignment operators work from right to left, so what your code is actually doing is equivalent to:
$c = $c & $d;
$b = $b & $c;
if ($a == $b) { ...
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To check if 4 variables are the same you will need to do something like:
if ($a == ($b == ($c == $d))) {
echo "true";
} else {
echo "false";
} |
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coopster
msg:3912516 | 11:57 am on May 13, 2009 (gmt 0) |
That won't work either. Working from within the parenthesis, $c == $d will return boolean TRUE as the value of variable $c which is "test" does indeed equal the value of variable $d which is "test". The return value of that expression is boolean TRUE. Now you have ...
if ($a == ($b == ((bool) TRUE))) {
... and so the statement will indeed return true.
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penders
msg:3912700 | 4:49 pm on May 13, 2009 (gmt 0) |
| if ($a == ($b == ((bool) TRUE))) { |
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Dang, of course - thanks! In that case, it's just the usual...
if (($a == $b) && ($b == $c) && ($c == $d)) {
echo "true\n";
} else {
echo "false\n";
} |
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Anything 'quicker'? IMHO, if you need to check for equality between many variables then I'd use an alternative memory structure eg. an array.
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coopster
msg:3912843 | 7:11 pm on May 13, 2009 (gmt 0) |
I agree, that was my first thought :) You could probably get fancy with something like array_diff and array_filter, perhaps array_values thrown in ... just some initial thoughts that raced through my mind.
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pinterface
msg:3913316 | 8:24 am on May 14, 2009 (gmt 0) |
If you want to use an array_* function, you'd probably want array_unique [us.php.net]:
if (1 == sizeof(array_unique([$a, $b, $c, $d]))) {
// ...
}
Something like that.
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