php-general Digest 8 Jan 2012 15:53:09 -0000 Issue 7640
Topics (messages 316211 through 316219):
Variable Troubleshooting Code
316211 by: Donovan Brooke
316212 by: David Courtin
Strange foreach reference issue
316213 by: Tim Behrendsen
316214 by: Stephen
316215 by: Matijn Woudt
316216 by: Tim Behrendsen
316217 by: Stephen
316218 by: Tim Behrendsen
316219 by: Adi Mutu
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----------------------------------------------------------------------
--- Begin Message ---
Hello!,
I work in another language mostly and often develop while displaying
variables (post,get,and defined) and their values at the bottom of the
page or in specific places. So, I thought I'd forward my PHP version as
an effort of good Karma to the list perhaps! ;-)
Below is 2 simple functions that are helpful for troubleshooting while
developing. Just place this code into a .php file and require it at the
top of any PHP page. Then, at the bottom of the page, or in a specific
(more pertinent) location, call the functions with something like this:
------------
<?PHP
//troubleshooting code
print '<br /><b>Testing:</b><p>';
print htmlentities(list_formvars());
print htmlentities(list_vars(get_defined_vars()));
print '</p>';
?>
-------------
Optionally, you can call only specific naming conventions of your
variables (if you use them).. ie:
print htmlentities(list_vars(get_defined_vars(),'t_'));
The above will display all defined vars such as:
t_name=<value>
t_city=<value>
t_address=<value>
etc..
Code:
-----------------------------------
/*
FUNCTION NAME: list_formvars
INPUT: optional <begins with> var
OUTPUT: <Name> = <Value> <br />
<Name> = <Value> <br />
USE: For troubleshooting code
Example Use:
list_formvars();
list_formvars('f_a');
*/function list_formvars($pmatch = null) {
print "<br /><b>'get' Vars:</b><br />";
foreach ($_GET as $key => $value) {
if (isset($pmatch)) {
if (substr($key,0,strlen($pmatch)) == $pmatch) {
print "$key = $value<br />";
}
} else {
print "$key = $value<br />";
}
}
print "<br /><b>'post' Vars:</b><br />";
foreach ($_POST as $key => $value) {
if (isset($pmatch)) {
if (substr($key,0,strlen($pmatch)) == $pmatch) {
print "$key = $value<br />";
}
} else {
print "$key = $value<br />";
}
}
}/*
FUNCTION NAME: list_vars
INPUT: get_defined_vars(),<begins with> match
OUTPUT: <Name> = <Value> <br />
<Name> = <Value> <br />
USE: For troubleshooting code
Example Use:
list_vars(get_defined_vars());
list_vars(get_defined_vars(),'t_');
*/function list_vars($a_vars,$pmatch = null) {
print "<br /><b>'defined' Vars:</b><br />";
foreach ($a_vars as $key => $value) {
if (isset($pmatch)) {
if (substr($key,0,strlen($pmatch)) == $pmatch) {
print "$key = $value<br />";
}
} else {
print "$key = $value<br />";
}
}
}
------------------------------------------------
Cheers,
Donovan
P.S. Always open to good criticism if you peeps see something that can
be written better.. this is about my 3rd PHP project only... so, still
heavily learning ;-)
--
D Brooke
--- End Message ---
--- Begin Message ---
Hi,
some pretty natives php functions exists to do the job :
var_export — Outputs or returns a parsable string representation of a variable
debug_zval_dump — Dumps a string representation of an internal zend value to
output
var_dump — Dumps information about a variable
print_r — Prints human-readable information about a variable
echo '<pre>';
print_r( array | object );
echo '</pre>';
Regards.
Le 7 janv. 2012 à 19:00, Donovan Brooke a écrit :
> Hello!,
> I work in another language mostly and often develop while displaying
> variables (post,get,and defined) and their values at the bottom of the page
> or in specific places. So, I thought I'd forward my PHP version as an effort
> of good Karma to the list perhaps! ;-)
>
> Below is 2 simple functions that are helpful for troubleshooting while
> developing. Just place this code into a .php file and require it at the top
> of any PHP page. Then, at the bottom of the page, or in a specific (more
> pertinent) location, call the functions with something like this:
>
> ------------
> <?PHP
> //troubleshooting code
> print '<br /><b>Testing:</b><p>';
>
> print htmlentities(list_formvars());
>
> print htmlentities(list_vars(get_defined_vars()));
>
> print '</p>';
> ?>
> -------------
>
> Optionally, you can call only specific naming conventions of your variables
> (if you use them).. ie:
>
> print htmlentities(list_vars(get_defined_vars(),'t_'));
>
> The above will display all defined vars such as:
>
> t_name=<value>
> t_city=<value>
> t_address=<value>
>
> etc..
>
>
> Code:
> -----------------------------------
> /*
> FUNCTION NAME: list_formvars
> INPUT: optional <begins with> var
> OUTPUT: <Name> = <Value> <br />
> <Name> = <Value> <br />
> USE: For troubleshooting code
>
> Example Use:
> list_formvars();
> list_formvars('f_a');
>
> */function list_formvars($pmatch = null) {
> print "<br /><b>'get' Vars:</b><br />";
> foreach ($_GET as $key => $value) {
> if (isset($pmatch)) {
> if (substr($key,0,strlen($pmatch)) == $pmatch) {
> print "$key = $value<br />";
> }
> } else {
> print "$key = $value<br />";
> }
> }
>
> print "<br /><b>'post' Vars:</b><br />";
> foreach ($_POST as $key => $value) {
> if (isset($pmatch)) {
> if (substr($key,0,strlen($pmatch)) == $pmatch) {
> print "$key = $value<br />";
> }
> } else {
> print "$key = $value<br />";
> }
> }
> }/*
> FUNCTION NAME: list_vars
> INPUT: get_defined_vars(),<begins with> match
> OUTPUT: <Name> = <Value> <br />
> <Name> = <Value> <br />
> USE: For troubleshooting code
>
> Example Use:
> list_vars(get_defined_vars());
> list_vars(get_defined_vars(),'t_');
> */function list_vars($a_vars,$pmatch = null) {
> print "<br /><b>'defined' Vars:</b><br />";
> foreach ($a_vars as $key => $value) {
> if (isset($pmatch)) {
> if (substr($key,0,strlen($pmatch)) == $pmatch) {
> print "$key = $value<br />";
> }
> } else {
> print "$key = $value<br />";
> }
> }
> }
> ------------------------------------------------
>
> Cheers,
> Donovan
>
>
> P.S. Always open to good criticism if you peeps see something that can be
> written better.. this is about my 3rd PHP project only... so, still heavily
> learning ;-)
>
>
> --
> D Brooke
>
> --
> PHP General Mailing List (http://www.php.net/)
> To unsubscribe, visit: http://www.php.net/unsub.php
>
--- End Message ---
--- Begin Message ---
Hello,
This sure looks like a bug, but maybe there's some subtlety going on
that I don't understand, so I would appreciate some insight. After much
debugging, I tracked down a bug in my code to this test program. My PHP
version is 5.3.3, running under Fedora Linux.
<?php
$row_list = array(
array(
'Title' => 'Title #1',
),
array(
'Title' => 'Title #2',
),
array(
'Title' => 'Title #3',
) );
print " Rows at start: " . print_r($row_list, true);
foreach ($row_list as $idx => &$row) {
print "Title A $idx: {$row['Title']}\n";
}
print " Rows are now: " . print_r($row_list, true);
foreach ($row_list as $idx => $row) {
print "Title B $idx: {$row['Title']}\n";
}
?>
When you run the program, it gives the following output:
------------------------------------------
Rows at start: Array
(
[0] => Array
(
[Title] => Title #1
)
[1] => Array
(
[Title] => Title #2
)
[2] => Array
(
[Title] => Title #3
)
)
Title A 0: Title #1
Title A 1: Title #2
Title A 2: Title #3
Rows are now: Array
(
[0] => Array
(
[Title] => Title #1
)
[1] => Array
(
[Title] => Title #2
)
[2] => Array
(
[Title] => Title #3
)
)
Title B 0: Title #1
Title B 1: Title #2
Title B 2: Title #2
------------------------------------------
Note that the second foreach repeats the second row, even though the
index is correct and the print_r shows things as correct.
Now, if you change the name of the reference variable from '$row' to
'$rowx' (for example), things will work. So clearly there's some issue
with $row being previously used as a reference that's "contaminating"
the subsequent use of $row in the foreach. If there's some logic to
this, it's escaping me.
Any insight on this would be appreciated.
Regards,
Tim Behrendsen
--- End Message ---
--- Begin Message ---
I cut and pasted your code and got the same result.
I flipped the two foreach blocks and got the expected results.
I deleted the first block and copied the second, then updated the
string. I got this. I can't explain.
<?php
$row_list = array(
array(
'Title' => 'Title #1',
),
array(
'Title' => 'Title #2',
),
array(
'Title' => 'Title #3',
) );
print " Rows are: " . print_r($row_list, true);
foreach ($row_list as $idx => $row) {
print "Title A $idx: {$row['Title']}\n";
}
print " Rows are now: " . print_r($row_list, true);
foreach ($row_list as $idx => $row) {
print "Title B $idx: {$row['Title']}\n";
}
Rows are: Array
(
[0] => Array
(
[Title] => Title #1
)
[1] => Array
(
[Title] => Title #2
)
[2] => Array
(
[Title] => Title #3
)
)
Title A 0: Title #1
Title A 1: Title #2
Title A 2: Title #3
Rows are now: Array
(
[0] => Array
(
[Title] => Title #1
)
[1] => Array
(
[Title] => Title #2
)
[2] => Array
(
[Title] => Title #3
)
)
Title B 0: Title #1
Title B 1: Title #2
Title B 2: Title #3
On 12-01-07 06:29 PM, Tim Behrendsen wrote:
Hello,
This sure looks like a bug, but maybe there's some subtlety going on
that I don't understand, so I would appreciate some insight. After
much debugging, I tracked down a bug in my code to this test program.
My PHP version is 5.3.3, running under Fedora Linux.
<?php
$row_list = array(
array(
'Title' => 'Title #1',
),
array(
'Title' => 'Title #2',
),
array(
'Title' => 'Title #3',
) );
print " Rows at start: " . print_r($row_list, true);
foreach ($row_list as $idx => &$row) {
print "Title A $idx: {$row['Title']}\n";
}
print " Rows are now: " . print_r($row_list, true);
foreach ($row_list as $idx => $row) {
print "Title B $idx: {$row['Title']}\n";
}
?>
When you run the program, it gives the following output:
------------------------------------------
Rows at start: Array
(
[0] => Array
(
[Title] => Title #1
)
[1] => Array
(
[Title] => Title #2
)
[2] => Array
(
[Title] => Title #3
)
)
Title A 0: Title #1
Title A 1: Title #2
Title A 2: Title #3
Rows are now: Array
(
[0] => Array
(
[Title] => Title #1
)
[1] => Array
(
[Title] => Title #2
)
[2] => Array
(
[Title] => Title #3
)
)
Title B 0: Title #1
Title B 1: Title #2
Title B 2: Title #2
------------------------------------------
Note that the second foreach repeats the second row, even though the
index is correct and the print_r shows things as correct.
Now, if you change the name of the reference variable from '$row' to
'$rowx' (for example), things will work. So clearly there's some issue
with $row being previously used as a reference that's "contaminating"
the subsequent use of $row in the foreach. If there's some logic to
this, it's escaping me.
Any insight on this would be appreciated.
Regards,
Tim Behrendsen
--- End Message ---
--- Begin Message ---
On Sun, Jan 8, 2012 at 12:29 AM, Tim Behrendsen <t...@behrendsen.com> wrote:
> Hello,
>
> This sure looks like a bug, but maybe there's some subtlety going on that I
> don't understand, so I would appreciate some insight. After much debugging,
> I tracked down a bug in my code to this test program. My PHP version is
> 5.3.3, running under Fedora Linux.
>
> <?php
> $row_list = array(
> array(
> 'Title' => 'Title #1',
> ),
> array(
> 'Title' => 'Title #2',
> ),
> array(
> 'Title' => 'Title #3',
> ) );
>
> print " Rows at start: " . print_r($row_list, true);
> foreach ($row_list as $idx => &$row) {
Why is there an '&' before $row here? That seems like the problem to me..
Matijn
--- End Message ---
--- Begin Message ---
On 1/7/2012 4:18 PM, Matijn Woudt wrote:
On Sun, Jan 8, 2012 at 12:29 AM, Tim Behrendsen<t...@behrendsen.com> wrote:
Hello,
This sure looks like a bug, but maybe there's some subtlety going on that I
don't understand, so I would appreciate some insight. After much debugging,
I tracked down a bug in my code to this test program. My PHP version is
5.3.3, running under Fedora Linux.
<?php
$row_list = array(
array(
'Title' => 'Title #1',
),
array(
'Title' => 'Title #2',
),
array(
'Title' => 'Title #3',
) );
print " Rows at start: " . print_r($row_list, true);
foreach ($row_list as $idx => &$row) {
Why is there an '&' before $row here? That seems like the problem to me..
Matijn
When you use an ampersand on the variable, that creates a reference to
the array elements, allowing you to potentially change the array
elements themselves (which I'm not doing here).
http://www.php.net/manual/en/control-structures.foreach.php
I do notice in the manual that it says, "Reference of a $value and the
last array element remain even after the foreach loop. It is recommended
to destroy it by unset()." But that doesn't really explain why it
contaminates the next foreach loop in such an odd way. You would think
that the $row in the second loop would be assigned a non-reference value.
Tim
--- End Message ---
--- Begin Message ---
On 12-01-07 07:30 PM, Tim Behrendsen wrote:
When you use an ampersand on the variable, that creates a reference to
the array elements, allowing you to potentially change the array
elements themselves (which I'm not doing here).
http://www.php.net/manual/en/control-structures.foreach.php
I do notice in the manual that it says, "Reference of a $value and the
last array element remain even after the foreach loop. It is
recommended to destroy it by unset()." But that doesn't really explain
why it contaminates the next foreach loop in such an odd way. You
would think that the $row in the second loop would be assigned a
non-reference value.
Tim
Tim,
You are using the &$variable in an unintended (by PHP designers), and I
suggest undefined manner.
So the outcome cannot, but definition be explained.
Was this intended, and what were you trying to accomplish?
Stephen
--- End Message ---
--- Begin Message ---
On 1/7/2012 4:44 PM, Stephen wrote:
On 12-01-07 07:30 PM, Tim Behrendsen wrote:
When you use an ampersand on the variable, that creates a reference
to the array elements, allowing you to potentially change the array
elements themselves (which I'm not doing here).
http://www.php.net/manual/en/control-structures.foreach.php
I do notice in the manual that it says, "Reference of a $value and
the last array element remain even after the foreach loop. It is
recommended to destroy it by unset()." But that doesn't really
explain why it contaminates the next foreach loop in such an odd way.
You would think that the $row in the second loop would be assigned a
non-reference value.
Tim
Tim,
You are using the &$variable in an unintended (by PHP designers), and
I suggest undefined manner.
So the outcome cannot, but definition be explained.
Was this intended, and what were you trying to accomplish?
Stephen
In the real code, I just happen to use the same variable name first as a
reference, and then as a normal non-reference, and was getting the
mysterious duplicate rows.
I think I'm using everything in a completely reasonable way; the second
foreach is reassigning the loop variable. Nothing that comes before
using that variable ought to cause undefined behavior. The warning in
the manual is about using the loop variable as a reference after exiting
the loop, but I'm not doing that. I'm reassigning it, exactly as if I
just decided to do a straight assignment of "$row"....
Ah ha, wait a minute, that's the key. OK, this is making more sense.
The first loop is leaving a reference to the final element. But then the
second foreach is doing a straight assignment to the $row variable, but
$row is a reference to the final element. So the foreach is assigning
its iterated value to the final element of the array, instead of a
normal variable.
OK, I understand the logic now. The world now makes sense. The moral is
always unset the iterator variable when doing foreach with a reference,
like the manual says. :)
Thanks for everyone's help.
Tim
--- End Message ---
--- Begin Message ---
You can see here some nice pics, it's exactly as you said.
http://schlueters.de/blog/archives/141-References-and-foreach.html
________________________________
From: Tim Behrendsen <t...@behrendsen.com>
To: php-gene...@lists.php.net
Cc: Stephen <stephe...@rogers.com>; Matijn Woudt <tijn...@gmail.com>
Sent: Sunday, January 8, 2012 3:01 AM
Subject: Re: [PHP] Strange foreach reference issue
On 1/7/2012 4:44 PM, Stephen wrote:
> On 12-01-07 07:30 PM, Tim Behrendsen wrote:
>>
>> When you use an ampersand on the variable, that creates a reference to the
>> array elements, allowing you to potentially change the array elements
>> themselves (which I'm not doing here).
>>
>> http://www.php.net/manual/en/control-structures.foreach.php
>>
>> I do notice in the manual that it says, "Reference of a $value and the last
>> array element remain even after the foreach loop. It is recommended to
>> destroy it by unset()." But that doesn't really explain why it contaminates
>> the next foreach loop in such an odd way. You would think that the $row in
>> the second loop would be assigned a non-reference value.
>>
>> Tim
>>
> Tim,
>
> You are using the &$variable in an unintended (by PHP designers), and I
> suggest undefined manner.
>
> So the outcome cannot, but definition be explained.
>
> Was this intended, and what were you trying to accomplish?
>
> Stephen
In the real code, I just happen to use the same variable name first as a
reference, and then as a normal non-reference, and was getting the mysterious
duplicate rows.
I think I'm using everything in a completely reasonable way; the second foreach
is reassigning the loop variable. Nothing that comes before using that variable
ought to cause undefined behavior. The warning in the manual is about using the
loop variable as a reference after exiting the loop, but I'm not doing that.
I'm reassigning it, exactly as if I just decided to do a straight assignment of
"$row"....
Ah ha, wait a minute, that's the key. OK, this is making more sense.
The first loop is leaving a reference to the final element. But then the second
foreach is doing a straight assignment to the $row variable, but $row is a
reference to the final element. So the foreach is assigning its iterated value
to the final element of the array, instead of a normal variable.
OK, I understand the logic now. The world now makes sense. The moral is always
unset the iterator variable when doing foreach with a reference, like the
manual says. :)
Thanks for everyone's help.
Tim
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--- End Message ---
