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How to walk array and delete matched elements?

I'm kind of lost on this one - I need to modify 2 files based on user input:

$data_array = file($data_file );
$counter_array = file($counter_f ile);
// There is a line-for-line relationship between the data and counter files
//for example, if the 3rd line in the counter file is deleted,
//so also must the 3rd line of the data file be deleted.
// Each line of the data_file has 4 items:
//date|ip_address |user_id|url
for ( $i=0; $i < count($data_arr ay); $i++ )
$data_line = fgets($data_arr ay); //look at each line in data_array
$data = explode("|",$da ta_line);
if ( $data[1] = $ip ) //$ip is user input
{
array_pop($data _array, $data_line);
array_pop($coun ter_array[$i];
//not sure array_pop is correct function here - the manual says this
//will pop element from the bottom of the array, but I need
//to delete this particular element from the middle of the array.
//What is the best way to do this?
}

The goal is to create 2 new files. If the original files look like this:

[data_file]
3/4/04|20.123.112.2 1|grebos|http://www.asc.com
6/5/04|183.40.99.14 |boris|http://www.asc.com
7/16/04|133.73.115.2 9|grebos|http://www.asc.com

[counter file]
2345
1356
5466

and the user selected to remove IP 183.40.99.14, then the new files should
look like this:

[data_file]
3/4/04|20.123.112.2 1|grebos|http://www.asc.com
7/16/04|133.73.115.2 9|grebos|http://www.asc.com

[counter file]
2345
5466

I'm still kind of green when it comes to working with arrays... any help is
appreciated... Thanks.
Jul 17 '05 #1
19 3705
deko <ww************ *************** ****@nospam.com > wrote:
I'm kind of lost on this one - I need to modify 2 files based on user input:

8< -- long snip -- >8

<http://de3.php.net/array_splice> should do the job.

--
Simon Stienen <http://dangerouscat.ne t> <http://slashlife.de>
»What you do in this world is a matter of no consequence,
The question is, what can you make people believe that you have done.«
-- Sherlock Holmes in "A Study in Scarlet" by Sir Arthur Conan Doyle
Jul 17 '05 #2
> <http://de3.php.net/array_splice> should do the job.

Yes, but when the matched element appears twice in a row (that is, in two
lines immediately following each other in datafile.txt), the second one is
not removed from the array. I think this is because the array pointer is
being reset with each loop. Any suggestions on how to correct this?

$data_array = file(datafile.t xt);
$counter_file = file(counterfil e.txt);
//$ip = user defined

for ( $i=0; $i < count($data_arr ay); $i++ )
{
$data_line = $data_array[$i];
$data = explode("|", $data_line); //data_line format:
date|ip_address |user_id|url
if( in_array($ip, $data) )
{
array_splice($d ata_array,$i,1) ;
array_splice($c ounter_array,$i ,1);
}
}
Jul 17 '05 #3
deko <ww************ *************** ****@nospam.com > wrote:
<http://de3.php.net/array_splice> should do the job.


Yes, but when the matched element appears twice in a row (that is, in two
lines immediately following each other in datafile.txt), the second one is
not removed from the array. I think this is because the array pointer is
being reset with each loop. Any suggestions on how to correct this?

$data_array = file(datafile.t xt);
$counter_file = file(counterfil e.txt);
//$ip = user defined

for ( $i=0; $i < count($data_arr ay); $i++ )
{
$data_line = $data_array[$i];
$data = explode("|", $data_line); //data_line format:
date|ip_address |user_id|url
if( in_array($ip, $data) )
{
array_splice($d ata_array,$i,1) ;
array_splice($c ounter_array,$i ,1);
}
}


You mustn't increment after removing an element:

if x == 'b' || x == 'c' -> remove:

i=0.
A B C D E
^-- not removed, i->1

i=1
A B C D E
^-- remove, i->2, data->A C D E

i=2
A C D E
^-- oops, missed the one which fills the hole the previosly deleted
element left...

--
Simon Stienen <http://dangerouscat.ne t> <http://slashlife.de>
»What you do in this world is a matter of no consequence,
The question is, what can you make people believe that you have done.«
-- Sherlock Holmes in "A Study in Scarlet" by Sir Arthur Conan Doyle
Jul 17 '05 #4
"deko" <ww************ *************** ****@nospam.com > wrote in message
news:bG******** *******@newssvr 13.news.prodigy .com...
I'm kind of lost on this one - I need to modify 2 files based on user input:
$data_array = file($data_file );
$counter_array = file($counter_f ile);
// There is a line-for-line relationship between the data and counter files //for example, if the 3rd line in the counter file is deleted,
//so also must the 3rd line of the data file be deleted.
// Each line of the data_file has 4 items:
//date|ip_address |user_id|url
for ( $i=0; $i < count($data_arr ay); $i++ )
$data_line = fgets($data_arr ay); //look at each line in data_array
$data = explode("|",$da ta_line);
if ( $data[1] = $ip ) //$ip is user input
{
array_pop($data _array, $data_line);
array_pop($coun ter_array[$i];
//not sure array_pop is correct function here - the manual says this
//will pop element from the bottom of the array, but I need
//to delete this particular element from the middle of the array.
//What is the best way to do this?
}

The goal is to create 2 new files. If the original files look like this:

[data_file]
3/4/04|20.123.112.2 1|grebos|http://www.asc.com
6/5/04|183.40.99.14 |boris|http://www.asc.com
7/16/04|133.73.115.2 9|grebos|http://www.asc.com

[counter file]
2345
1356
5466

and the user selected to remove IP 183.40.99.14, then the new files should
look like this:

[data_file]
3/4/04|20.123.112.2 1|grebos|http://www.asc.com
7/16/04|133.73.115.2 9|grebos|http://www.asc.com

[counter file]
2345
5466

I'm still kind of green when it comes to working with arrays... any help is appreciated... Thanks.


The function you need is array_filter().
Jul 17 '05 #5
> The function you need is array_filter().

Well, I came up with the below code which is kind of a brute force way to do
it - but it works.
I looked up array_filter in the manual - perhaps it could be used in place
of the first if statement?

<?php
$data_file = "/path/to/data.txt";
$counter_file = "/path/to/counter.txt";
//need to reverse arrays because files are not the same length
//but there is a line-to-line relationship starting from the bottom
$data_array_asc ending = file($data_file );
$data_array = array_reverse($ data_array_asce nding);
$counter_array_ ascending = file($counter_f ile);
$counter_array = array_reverse($ counter_array_a scending);
$d = count($data_arr ay);
echo $d." elements in data_array log\n\n";
$ip = "68.122.35.157" ;
while ( $d > $e )
{
$d = count($data_arr ay);
for ( $i=0; $i < count($data_arr ay); $i++ )
{
$data_line = $data_array[$i];
$data = explode("|", $data_line);
//each line of data.txt has several elements separated by "|"
if( in_array($ip, $data) )
{
array_splice($d ata_array,$i,1) ;
array_splice($c ounter_array,$i ,1);
$c++;
$removed = $data_line.$rem oved;
}
}
$e = count($data_arr ay);
if ( $removed && $d == $e )
{
echo $c." elements removed:\n\n".$ removed."\n\n";
}
}
echo $e." elements in data_array\n\n" ;
$data_array_scr ubbed = array_reverse($ data_array);
$fp = fopen($data_fil e,"w");
foreach($data_a rray_scrubbed as $var)
{
fwrite($fp, $var);
}
fclose($fp);
$counter_array_ scrubbed = array_reverse($ counter_array);
$fp = fopen($counter_ file,"w");
foreach($counte r_array_scrubbe d as $var)
{
fwrite($fp, $var);
}
fclose($fp);
?>
Jul 17 '05 #6
"deko" <ww************ *************** ****@nospam.com > wrote in message
news:%t******** ********@newssv r13.news.prodig y.com...
The function you need is array_filter().
Well, I came up with the below code which is kind of a brute force way to

do it - but it works.
I looked up array_filter in the manual - perhaps it could be used in place
of the first if statement?


What I would do is this: Pass both arrays to array_map(), with null as the
callback function. You will end up with an array with the following
structure:

Array
(
[0] => Array
(
[0] => 3/4/04|20.123.112.2 1|grebos|http://www.asc.com
[1] => 2345
)

[1] => Array
(
[0] => 6/5/04|183.40.99.14 |boris|http://www.asc.com
[1] => 5466
)
)

Write a function that decides whether an element should be removed. It'll
need to get the IP address via a global variable because array_filter()
doesn't let you pass data to the callback. Or if you want to be more
elegant, define a lamda function with create_function () that looks for that
specific IP. Anyway, the function would look something like this:

function NotMatchIP($a) {
global $ip;
$data_line = $a[0];
$data = explode("|", $data_line);
return ($ip != $data[1]);
}

Pass the combined array to array_filter() using this function as the
callback. The array returned will contain the scrubbed content for both
files. Just loop through it and write to both at the same time.

The trick here is the use of array_map(). Working with one array is
obviously easier than two.
Jul 17 '05 #7
> What I would do is this: Pass both arrays to array_map(), with null as the
callback function. You will end up with an array with the following
structure:

Array
(
[0] => Array
(
[0] => 3/4/04|20.123.112.2 1|grebos|http://www.asc.com
[1] => 2345
)

[1] => Array
(
[0] => 6/5/04|183.40.99.14 |boris|http://www.asc.com
[1] => 5466
)
)
So, this is a multi-dimensional array, correct?
Write a function that decides whether an element should be removed. It'll
need to get the IP address via a global variable because array_filter()
doesn't let you pass data to the callback. Or if you want to be more
elegant, define a lamda function with create_function () that looks for that specific IP. Anyway, the function would look something like this:

function NotMatchIP($a) {
global $ip;
$data_line = $a[0];
$data = explode("|", $data_line);
return ($ip != $data[1]);
}
is this a lamda function? What is a lamda function?

Pass the combined array to array_filter() using this function as the
callback. The array returned will contain the scrubbed content for both
files. Just loop through it and write to both at the same time.
This sounds interesting - I'll give it a shot.
The trick here is the use of array_map(). Working with one array is
obviously easier than two.

Jul 17 '05 #8
deko <ww************ *************** ****@nospam.com > wrote:
What I would do is this: Pass both arrays to array_map(), with null as the
callback function. You will end up with an array with the following
structure:

Array
(
[0] => Array
(
[0] => 3/4/04|20.123.112.2 1|grebos|http://www.asc.com
[1] => 2345
)

[1] => Array
(
[0] => 6/5/04|183.40.99.14 |boris|http://www.asc.com
[1] => 5466
)
)


So, this is a multi-dimensional array, correct?


Correct.
Write a function that decides whether an element should be removed. It'll
need to get the IP address via a global variable because array_filter()
doesn't let you pass data to the callback. Or if you want to be more
elegant, define a lamda function with create_function () that looks for
that specific IP. Anyway, the function would look something like this:

function NotMatchIP($a) {
global $ip;
$data_line = $a[0];
$data = explode("|", $data_line);
return ($ip != $data[1]);
}


is this a lamda function? What is a lamda function?


No. As soon as you use the control word "function" you have a named
function (here: NotMatchIP). A lambda function is an unnamed function,
created by create_function () and *only* by create_function ().
While you can call a named function using it's name (here:
MotMatchIp($foo )), you can't call a lambda function the same way, since it
has no name. Instead, you have a variable containing the function, calling
the variable with your parameters:
-----BEGIN PHP CODE BLOCK-----
$my_unnamed_fun ction = create_function ('$x','echo $x+1;');
$my_unnamed_fun ction(5); // outputs 6. notice the preceding dollar sign
$echo_next_inte ger = $my_unnamed_fun ction;
$echo_next_inte ger(17); // outputs 18.
------END PHP CODE BLOCK------

I am not sure about this, but I guess, that internally the concept of PHPs
"function pointers" is used, like in:
-----BEGIN PHP CODE BLOCK-----
$trigonomical_f unction = 'sin'; // string!
echo $trigonomical_f unction($x); // calls sin($x)
------END PHP CODE BLOCK------
Therefore echo $my_unnamed_fun ction should give you the internally used
name of the function. (Which is of no use, since it might change from one
parsing of the script to the next... It's just a technical detail.)

As you can see, you can "copy" the function to another variable, so you
could create whole bunches of functions, saving them in an array and
applying them one after another. All you have to do is to define a API of
parameters which will be used and returned:
-----BEGIN PHP CODE BLOCK-----
// define a function
function square($x) {
return $x*$x;
}

// list functions to use
$funcs = array(
'sin', // internal function
'square', // user-defined function
create_function ('$x','return $x*2') // lambda function
);

// output results
foreach ($funcs as $funcname)
echo $funcname . '(10) is: ' . $funcname(10) . chr(13);
------END PHP CODE BLOCK------
(Note: Every of these functions takes exactly one number.)

HTH
Simon
--
Simon Stienen <http://dangerouscat.ne t> <http://slashlife.de>
»What you do in this world is a matter of no consequence,
The question is, what can you make people believe that you have done.«
-- Sherlock Holmes in "A Study in Scarlet" by Sir Arthur Conan Doyle
Jul 17 '05 #9
> > is this a lamda function? What is a lamda function?

No. As soon as you use the control word "function" you have a named
function (here: NotMatchIP). A lambda function is an unnamed function,
created by create_function () and *only* by create_function ().
While you can call a named function using it's name (here:
MotMatchIp($foo )), you can't call a lambda function the same way, since it
has no name. Instead, you have a variable containing the function, calling
the variable with your parameters: .... snip ... I am not sure about this, but I guess, that internally the concept of PHPs
"function pointers" is used, like in: .... snip ... Therefore echo $my_unnamed_fun ction should give you the internally used
name of the function. (Which is of no use, since it might change from one
parsing of the script to the next... It's just a technical detail.)

As you can see, you can "copy" the function to another variable, so you
could create whole bunches of functions, saving them in an array and
applying them one after another. All you have to do is to define a API of
parameters which will be used and returned:


Thanks for the info - I appreciate the feedback.

The problem with using a multi-dimensional array is that the 2 files are
different lengths. I need to create both arrays individually to do stuff in
an earlier section of the script, so it's easy enough to reverse them and
start from the bottom. As long as the array keys stay in sync, it should
work...

$data_array_r = array_reverse($ data_array);
$counter_array_ r = array_reverse($ counter_array);
$d = count($data_arr ay_r) - 1; // there's a reason for -1
echo "Starting with ".$d." entries<br><br> ";
while ( $d > $s )
// $d>$s causes the while loop
//to run at least twice - so if there
//are 2 entries in a row in data_array
//that need to be spliced out,
//the second one isn't missed
//due to the array pointer reseting
//with each for loop.
{
$d = count($data_arr ay_r) - 1;
for ( $i=0; $i < $d; $i++ )
{
$data_line = $data_array_r[$i];
$data = explode("|", $data_line);
if( in_array($ip, $data) )
{
// here's where the 2 in a row problem arises
array_splice($d ata_array_r,$i, 1);
array_splice($c ounter_array_r, $i,1);
$n++;
$removed = $data_line."<br >".$removed;
}
}
$s = count($data_arr ay_r) - 1;
if ( $removed && $d == $s )
{
echo $n." entries removed:<br><br >".$removed."<b r>";
}
}
echo "Ending with ".$s." entries<br>";
Jul 17 '05 #10

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