| On the usage of "@" (error control operator) [message #178206] |
Wed, 23 May 2012 13:17  |
Leonardo Azpurua
Messages: 46
Registered: December 2010
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Hi,
A few weeks ago, I wrote this sentence:
@$retVal = $this->lastfetch[$ndx];
Yesterday, browsing the manual, I found this paragraph:
"PHP supports one error control operator: the at sign (@). _When prepended
to an expression_ in PHP, any error messages that might be generated by that
expression will be ignored."
and, a few lines further:
"A simple rule of thumb is: if you can take the value of something, you can
prepend the @ operator to it."
Since an assigment is not an expression, the required syntax should be:
$retVal = @$this->lastfetch[$ndx];
But both forms work.
Is there any reason to prefer one above the other?
--
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| Re: On the usage of "@" (error control operator) [message #178207 is a reply to message #178206] |
Wed, 23 May 2012 13:50  |
Jerry Stuckle
Messages: 2598
Registered: September 2010
Karma: 0
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Senior Member |
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On 5/23/2012 9:17 AM, Leonardo Azpurua wrote:
> Hi,
>
> A few weeks ago, I wrote this sentence:
>
> @$retVal = $this->lastfetch[$ndx];
>
> Yesterday, browsing the manual, I found this paragraph:
>
> "PHP supports one error control operator: the at sign (@). _When prepended
> to an expression_ in PHP, any error messages that might be generated by that
> expression will be ignored."
>
> and, a few lines further:
>
> "A simple rule of thumb is: if you can take the value of something, you can
> prepend the @ operator to it."
>
> Since an assigment is not an expression, the required syntax should be:
>
> $retVal = @$this->lastfetch[$ndx];
>
> But both forms work.
>
>
> Is there any reason to prefer one above the other?
>
> --
>
>
My preference is to not use it at all and fix the error.
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================
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| Re: On the usage of "@" (error control operator) [message #178208 is a reply to message #178206] |
Wed, 23 May 2012 14:12 |
Shake
Messages: 40
Registered: May 2012
Karma: 0
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Member |
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El 23/05/2012 15:17, Leonardo Azpurua escribió:
> Hi,
>
> A few weeks ago, I wrote this sentence:
>
> @$retVal = $this->lastfetch[$ndx];
>
> Yesterday, browsing the manual, I found this paragraph:
>
> "PHP supports one error control operator: the at sign (@). _When prepended
> to an expression_ in PHP, any error messages that might be generated by that
> expression will be ignored."
>
> and, a few lines further:
>
> "A simple rule of thumb is: if you can take the value of something, you can
> prepend the @ operator to it."
>
> Since an assigment is not an expression, the required syntax should be:
>
> $retVal = @$this->lastfetch[$ndx];
>
> But both forms work.
>
>
> Is there any reason to prefer one above the other?
>
Both forms works, but not both forms are the same:
$retVal = @$this->lastfetch[$ndx];
(....errors ignored....)
@$retVal = $this->lastfetch[$ndx];
(.........Errors ignored.........)
Perhaps in some cases "$retVal" could throw a type casting error or
something of this kind.
Rgds.
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| Re: On the usage of "@" (error control operator) [message #178209 is a reply to message #178207] |
Wed, 23 May 2012 14:49 |
Leonardo Azpurua
Messages: 46
Registered: December 2010
Karma: 0
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Member |
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"Jerry Stuckle" <jstucklex(at)attglobal(dot)net> escribió en el mensaje
news:jpiq01$km7$1(at)dont-email(dot)me...
>> [snip]
>> Since an assigment is not an expression, the required syntax should be:
>>
>> $retVal = @$this->lastfetch[$ndx];
>>
>> But both forms work.
>>
>>
>> Is there any reason to prefer one above the other?
>>
>> --
>>
>>
>
> My preference is to not use it at all and fix the error.
>
Hi,
In this case there is no error to fix.
I am writing (mostly for study purposes) a Web Interface to the reports of a
business system of mine. This reports are generated from a user-generated
script contained in a text file.
Data items may come from several sources, like script defined variables,
predefined variables, input parameters, database columns or script defined
formulas.
So, I must search an identifier in several associative arrays. And trying to
access an array element with an invalid index triggers an error.
An alternative would be to walk the array comparing each key with the
desired identifier, but it means more code and, probably, less efficiency
(even with the overhead of the @ operator).
Anyway, any advice regarding a cleaner way to do this, will be very
appreciated.
Thanks!
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| Re: On the usage of "@" (error control operator) [message #178210 is a reply to message #178208] |
Wed, 23 May 2012 14:52 |
Leonardo Azpurua
Messages: 46
Registered: December 2010
Karma: 0
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Member |
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"Shake" <QUITAESTO(at)QUITAESTO(dot)NOES> escribió en el mensaje
news:jpir8f$til$1(at)dont-email(dot)me...
> El 23/05/2012 15:17, Leonardo Azpurua escribió:
>> Hi,
>>
>> A few weeks ago, I wrote this sentence:
>>
>> @$retVal = $this->lastfetch[$ndx];
>>
>> Yesterday, browsing the manual, I found this paragraph:
>>
>> "PHP supports one error control operator: the at sign (@). _When
>> prepended
>> to an expression_ in PHP, any error messages that might be generated by
>> that
>> expression will be ignored."
>>
>> and, a few lines further:
>>
>> "A simple rule of thumb is: if you can take the value of something, you
>> can
>> prepend the @ operator to it."
>>
>> Since an assigment is not an expression, the required syntax should be:
>>
>> $retVal = @$this->lastfetch[$ndx];
>>
>> But both forms work.
>>
>>
>> Is there any reason to prefer one above the other?
>>
>
> Both forms works, but not both forms are the same:
>
>
> $retVal = @$this->lastfetch[$ndx];
> (....errors ignored....)
>
> @$retVal = $this->lastfetch[$ndx];
> (.........Errors ignored.........)
>
>
> Perhaps in some cases "$retVal" could throw a type casting error or
> something of this kind.
Thanks.
Is there any chance that a type casting error occurs in such a statement?
--
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| Re: On the usage of "@" (error control operator) [message #178213 is a reply to message #178210] |
Wed, 23 May 2012 15:11 |
Shake
Messages: 40
Registered: May 2012
Karma: 0
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Member |
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El 23/05/2012 16:52, Leonardo Azpurua escribió:
>>
>> Perhaps in some cases "$retVal" could throw a type casting error or
>> something of this kind.
>
> Thanks.
>
> Is there any chance that a type casting error occurs in such a statement?
>
Don't know. Was only an Idea... a suspect, that that could happen (not
necesarily with type casting).
Rgds.
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| Re: On the usage of "@" (error control operator) [message #178214 is a reply to message #178213] |
Wed, 23 May 2012 15:14 |
Leonardo Azpurua
Messages: 46
Registered: December 2010
Karma: 0
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Member |
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"Shake" <QUITAESTO(at)QUITAESTO(dot)NOES> escribió en el mensaje
news:jpiuno$kih$1(at)dont-email(dot)me...
> El 23/05/2012 16:52, Leonardo Azpurua escribió:
>>>
>>> Perhaps in some cases "$retVal" could throw a type casting error or
>>> something of this kind.
>>
>> Thanks.
>>
>> Is there any chance that a type casting error occurs in such a statement?
>>
>
> Don't know. Was only an Idea... a suspect, that that could happen (not
> necesarily with type casting).
Yup. Got the idea.
Thanks, again.
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| Re: On the usage of "@" (error control operator) [message #178215 is a reply to message #178209] |
Wed, 23 May 2012 16:12 |
Jerry Stuckle
Messages: 2598
Registered: September 2010
Karma: 0
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Senior Member |
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On 5/23/2012 10:49 AM, Leonardo Azpurua wrote:
> "Jerry Stuckle"<jstucklex(at)attglobal(dot)net> escribió en el mensaje
> news:jpiq01$km7$1(at)dont-email(dot)me...
>>> [snip]
>>> Since an assigment is not an expression, the required syntax should be:
>>>
>>> $retVal = @$this->lastfetch[$ndx];
>>>
>>> But both forms work.
>>>
>>>
>>> Is there any reason to prefer one above the other?
>>>
>>> --
>>>
>>>
>>
>> My preference is to not use it at all and fix the error.
>>
>
> Hi,
>
> In this case there is no error to fix.
>
> I am writing (mostly for study purposes) a Web Interface to the reports of a
> business system of mine. This reports are generated from a user-generated
> script contained in a text file.
>
> Data items may come from several sources, like script defined variables,
> predefined variables, input parameters, database columns or script defined
> formulas.
>
> So, I must search an identifier in several associative arrays. And trying to
> access an array element with an invalid index triggers an error.
>
Then there is an error. So, the solution is to check to see if the
element exists before trying to access it.
> An alternative would be to walk the array comparing each key with the
> desired identifier, but it means more code and, probably, less efficiency
> (even with the overhead of the @ operator).
>
Maybe, maybe not. It depends on a lot of factors.
> Anyway, any advice regarding a cleaner way to do this, will be very
> appreciated.
>
> Thanks!
>
>
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================
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| Re: On the usage of "@" (error control operator) [message #178216 is a reply to message #178208] |
Wed, 23 May 2012 16:13 |
Jerry Stuckle
Messages: 2598
Registered: September 2010
Karma: 0
|
Senior Member |
|
|
On 5/23/2012 10:12 AM, Shake wrote:
> El 23/05/2012 15:17, Leonardo Azpurua escribió:
>> Hi,
>>
>> A few weeks ago, I wrote this sentence:
>>
>> @$retVal = $this->lastfetch[$ndx];
>>
>> Yesterday, browsing the manual, I found this paragraph:
>>
>> "PHP supports one error control operator: the at sign (@). _When
>> prepended
>> to an expression_ in PHP, any error messages that might be generated
>> by that
>> expression will be ignored."
>>
>> and, a few lines further:
>>
>> "A simple rule of thumb is: if you can take the value of something,
>> you can
>> prepend the @ operator to it."
>>
>> Since an assigment is not an expression, the required syntax should be:
>>
>> $retVal = @$this->lastfetch[$ndx];
>>
>> But both forms work.
>>
>>
>> Is there any reason to prefer one above the other?
>>
>
> Both forms works, but not both forms are the same:
>
>
> $retVal = @$this->lastfetch[$ndx];
> (....errors ignored....)
>
> @$retVal = $this->lastfetch[$ndx];
> (.........Errors ignored.........)
>
>
> Perhaps in some cases "$retVal" could throw a type casting error or
> something of this kind.
>
> Rgds.
What type casting error? Or are you just guessing?
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================
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|
|
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| Re: On the usage of "@" (error control operator) [message #178221 is a reply to message #178215] |
Wed, 23 May 2012 18:45 |
Leonardo Azpurua
Messages: 46
Registered: December 2010
Karma: 0
|
Member |
|
|
"Jerry Stuckle" <jstucklex(at)attglobal(dot)net> escribió en el mensaje
news:jpj296$bh7$1(at)dont-email(dot)me...
> On 5/23/2012 10:49 AM, Leonardo Azpurua wrote:
>> So, I must search an identifier in several associative arrays. And trying
>> to
>> access an array element with an invalid index triggers an error.
Hi,
I might have a valid index or not. And if it is valid, it could be valid on
one among several arrays.
Anyway, I just learnt that isset($arr[$ndx]) does not fire an error if $ndx
is not valid on $arr.
So, instead of
@$x = $arr[$ndx];
if (isset($x)) {
...
}
I should have written
if (isset($arr[$ndx])) {
$x = $arr[$ndx];
...
}
avoiding the rather ugly original construct.
Thanks!
--
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| Re: On the usage of "@" (error control operator) [message #178225 is a reply to message #178221] |
Wed, 23 May 2012 20:14 |
Jerry Stuckle
Messages: 2598
Registered: September 2010
Karma: 0
|
Senior Member |
|
|
On 5/23/2012 2:45 PM, Leonardo Azpurua wrote:
> "Jerry Stuckle"<jstucklex(at)attglobal(dot)net> escribió en el mensaje
> news:jpj296$bh7$1(at)dont-email(dot)me...
>> On 5/23/2012 10:49 AM, Leonardo Azpurua wrote:
>>> So, I must search an identifier in several associative arrays. And trying
>>> to
>>> access an array element with an invalid index triggers an error.
>
> Hi,
>
> I might have a valid index or not. And if it is valid, it could be valid on
> one among several arrays.
>
> Anyway, I just learnt that isset($arr[$ndx]) does not fire an error if $ndx
> is not valid on $arr.
>
> So, instead of
>
> @$x = $arr[$ndx];
> if (isset($x)) {
> ...
> }
>
> I should have written
>
> if (isset($arr[$ndx])) {
> $x = $arr[$ndx];
> ...
> }
>
> avoiding the rather ugly original construct.
>
> Thanks!
> --
>
>
Yup, that's what isset() is for. And this way looks a lot nicer, also :)
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================
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| Re: On the usage of "@" (error control operator) [message #178249 is a reply to message #178206] |
Thu, 24 May 2012 20:26 |
Thomas Mlynarczyk
Messages: 131
Registered: September 2010
Karma: 0
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Senior Member |
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Leonardo Azpurua schrieb:
> Since an assigment is not an expression
But it is in PHP! You can write, e.g.:
if ( is_file( $file = $dir . $name . $ext ) )
{
include $file;
}
Greetings,
Thomas
--
Ce n'est pas parce qu'ils sont nombreux à avoir tort qu'ils ont raison!
(Coluche)
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