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@PeterPan_321Nov 19.2018 — #Thanks guys. I have a LOT to learn about associative arrays, It didn't look like any of the sorting methods in the MANual would offer an easy fix, but that's probably because I'm just not understanding. In the meantime I came up with something that is probably an ugly kludge, but it works. In my original routine, in addition to building the three parallel arrays for the filenames, filepaths, and formatted time stamps, I added an array to hold the raw time (integer) stamps. So when that process completes, I do this... (please forgive my old school "c" mentality.)
$max = max($rawTimestamps);
$newtotal=0;
for ($i=0; $i < $total; $i++)
{
$lowest = min($rawTimestamps);
if ($lowest > $max) break; // stop when no more.
}
So what i did here is I recorded the maximum value in my $rawtimestamps array and started a $newtotal variable. Then the outer loop records the lowest timestamp value in that array, while the inner loop looks for all occurrences of that timestamp, and adds the index location ($j) where they were found to a new array called $indexes. After each one is found it replaces the original integer timestamp with a value greater than the recorded max value. That prevents it from ever being discovered again as the "lowest' value. (It also makes it easy to break out of the outer loop, when the lowest value found on the last pass exceeds to original max value!).
OK, this process destroys the rawtimestamps array, but I won't ever need it again after this. The newly built up array called $indexes now serves as a map. When I next display all my files and photos, I just have one added step, to use this map value to index all my other file data...
echo "<h1>$newtotal Image Files</h1>";
for ($i=0; $i < $newtotal; $i++)
{
$ix= $indexes[$i]; // get index to progressively older files
echo "<br><hr><h1>$filenames[$ix] $timestamps[$ix] <br></h1>";
echo "<img src='$filepaths[$ix]' style='width:100%;height:auto;'><br>";
}
}
I am sure that my lack of understanding of associative arrays has made this code uglier than it needs to be. But it works, so now I have a working reference. I'll definitely try the associative array method@Sempervivum suggested and see how much faster (or slower) it is. Thanks again!
By the way, the editor in the new Webdeveloper.com doesn't seem to have a button to properly format code snippets, so I'm just pasting them in and hoping for the best. But is there a proper way (or some proper tags) to better format code for posts?@PeterPan_321Nov 20.2018 — #@root#1597971 Much appreciated. What you said is new to me... working in C for web page actions. Probably because 90% of the time it needs to include an HTML form to offer some control, options, and defaults. All the examples I've seen of dealing with forms and server side processing always point me to PHP/Html combos. And while javascript has become plenty powerful too, the PHP variables are a reasonably safe way to have a basic password to, and compiled PHP seems to be very fast!
In the end, as I mentioned in my long winded post (LOL), I did come up with what I'd call a brute force solution. What I was looking for was, given an array of random timestamp integers, return another array whose elements contained indexes to progressively higher (or lower) elements in the first array. Kind of a re-mapping array. Thus, if i used that new mapping array to display consecutive photos in a loop, I could use the loop counter as an index to "look up" the next (older or younger) image index in the map, for display. I thought my double loop would be inefficient, But even testing with several hundreds of photos, the processing seemed instantaneous.
I just kept thinking there might be an existing sort routine to do what I did, and there probably is. But sometimes I waste a ton of time looking for some ready made class or function to simplify a task for me, and it the end it took less time to just "roll my own". My PHP coding often still does look like old school 'c', and aside from a few different rules, its basically the same, right?
I still wish I knew the proper way to post code on this board.
@cootheadNov 20.2018 — #
This has been answered here...
[url=https://www.webdeveloper.com/forum/d/383022-how-do-i-display-code]**[color=#069]How do I display code[/color] **[/url]
_coothead_@PeterPan_321Nov 20.2018 — #@coothead#1598026 Thanks again! I was hoping to try it on my previous posts, but it looks like the system won't let me re-edit days after the fact.@PeterPan_321Nov 20.2018 — #@root#1598030 No I haven't. I'm not lazy about learning, but I always have so many projects going that I end up learning new skills when I need them. I' ve barely scratched the surface in using SQL, and wouldn't know where to begin. But as long as I've solved the problem with 10 lines of code, I'm good with that. I think it also makes sense to solve problems the simplest way possible, wouldn't you agree? I mean, I know in the widows programming environment, I've seen coders pull in ExCell or create Acess databases just to do a few calculations (or in this case sorts). As I was working in the PHP environment, I'd have been willing to try existing PHP sort methods that accomplished what i wanted to do, and think i still can ONCE I master associative arrays. But I think pulling in databases services for such a small isolated task might be overkill for the time being. A good exercise for learning though!
Thanks again!@PeterPan_321Nov 21.2018 — #@Sempervivum#1598080
Would you be so kind as to give me an example, based on the problem I just solved via a different route? It will take some explaining so bear with me. I started with a two simple one dimensional arrays. One of filepaths to various image files, the other to unix time stamps for these same files. So a given index (let's say $i) could be used to look up the file path and timestamp.
Now, since I wanted to display the images in order of their ascending timestamps, I wrote the double loop I described earlier to create another simple array called $indexes, My "sort" routine progressively stored the index location to progressively older timestamps. So now, when I went to display the images, instead of just using a for() loop to progressively display the time stamps and images, I could take my index variable $i, and use it to "look up" the next index to be displayed in my "map" array...
$correctedIndex = $indexes($i);
So now, even though $i simply incremented from 0 to the total, my $correctedindex would ensure that the timestamp and image I pulled from the original arrays were in time-wise order.
So now, lets go back to that array i created with my sort routine. Again, it was a simple one dimensional array, filled with timestamps in random order. If I simply sorted that array, I would lose all the original index references I needed. But, maybe if if I had an associative array, where the integer timestamps were 'associated' with the filepath of each image, THEN if I sorted by the timestamps, I'd be able to do a "forEach" construct, and know that the timestamps and filepaths would be accessed in the order of the sort.
But all that is a concept in my head, and I've not been able to figure out how to implement it based on the online MANual for PHP associative arrays.@PeterPan_321Nov 21.2018 — #Thanks @Sempervivum#1598105 ! That multi_sort() does seem to work! I had to embed it in html code to test and upload it to my hosting co, because I have nothing that can run PHP at home. But it worked as you described, and I tried the SORT_DESC flag too, and see that I can opt to sort in descending order. And, after adding other parallel arrays to the call, it continued to work! Well writing my own was still a good exercise, but I'll your your method.
@root#1598118 - I still don't quite understand keys yet, which is why I'd asked for an example of associative array. Maybe ALL arrays in PHP are associative in the background? I don't know,, but given I was starting by getting each image's fullpath into a $filepaths array, and storing each file's timestamps in a separate $timestamps array, From what you said, I get the feeling i could have placed both items in a single associative array, with the timestamps as keys, and then sorting the array by keys. But I'm not sure how I would have done that, because I still don't quite understand how keys work, or what the => operator actually means. I can keep trying, but an example would be appreciated. I realize its something I really need to learn, but I'm having trouble grasping how it works from the online MANual or other examples I've seen.
@NogDogNov 21.2018 — #In some languages, you have arrays and hashes, where the "keys" in arrays are always integers (i.e. "indexes"), while hashes only have string keys. In PHP, there are only arrays, and they can use both string and integer keys interchangeably. Each of these is valid, though the "confusing_mess" is generally to be avoided (example in command line mode, thus those
@PeterPan_321Nov 21.2018 — #@Sempervivum#1598126 Excellent! Must try this!
So if I understand the above correctly...
1) the raw unix file time integer is the first item in the $fi array, which becomes the key.
2) I can then add several more items and use => symbols to 'associate' the given name (like "filename") with each subsequent item
3) as long as the key (raw timestamp) is unique, I can continue adding additional files this way.
If that is correct, some more questions...
1) what would I do now to "sort" the whole associated array now, by those keys?
2) Can this type of array still be indexed? such as for($i =0; i < count($fi); $i++) { do stuff}?, and would the returned array elements now be in order of the sorted keys?
3) within the loop, I could then access my elements as $fi[$i] => "filename" ? and have them accessed in timestamp sorted order?
4) and finally, an unrelated but possibly troublesome question. Wouldn't using the timestamp as a key mean multiple files with the same timestamp would get overwritten? If so, I'm thinking it might be better if a simple increment number was used as the key ($number++), and then add the raw timestamp integer as an associated element. I could still sort based on the "timestamp" element I choose, right? I understand the order of identical timestamps is undefined in a sort, as long as files aren't lost in the process.@PeterPan_321Nov 23.2018 — #Well I thank you all. I still have confusion and many unanswered questions, but I have a start and some good confirmations about the concepts of associative arrays.
One thing I still believe will be a flaw here. If I move to associative arrays for this little project and let timestamps be my keys, multiple images that have the same timestamp will be lost. Therefore, in addition to timestamps and filepaths I will have to add another item $count, that simply increments ($count++) and let that be the key since it will always be unique. So then I will have to figure out how to do my sort (or multisort) based on the key, but on on the 'timestamp' element rather than the key. Is that possible?
@PeterPan_321Nov 24.2018 — #
Well I confess you're right. But to be fair I've used arrays all my life and have been coding for many years, and have a level of proficiency in other languages. Its the properties of PHP arrays that have me confused. Part of the problem is that everyone that does fully understand are not always the best teachers, and the MANual for this language, though a good reference, is not the best teacher for learning the language from the ground up.
>
I don't understand that syntax. I would take that as a function named time() is being set equal to a number.
>
I understand the difference between a number and a string. But ordinary arrays referenced by position rather than key could also be an array of strings or other any objects. I don't think you're inferring that an array containing strings MUST be associative. Are you saying that arrays referenced by position could also be referenced by association?
>
I've seen that use of => for an associative array. So USING that syntax lets the compiler or interpreter know that you're intention is to use this array as an associative array?
Here's a yes/no question: can an associative array also be referenced by position? For the above, could array position 0 (or $arraydata[0] ) be used to reference the key 123456789 and the string "something happened? in a for() loop with positional indexes?
But how does that relate to my MY situation? I was dealing with the timestamps on files which only resolve to a second, so its possible for several files being continually uploaded to end up with identical timestamps. hence, I realized I could not use that timestamp as a key, because multiple files stored in the array using the same key reference would overwrite each other.
I'm beginning to understand, but few manuals these days (including the PHP MANual) is not written as well as the Kernighan and Ritchie C manual. What I need, really, is a good complete reference and teaching book like that. I can usually get enough from MANual and other examples via GOOGLE. But if I really want to master these concepts, such a complete reference would be better than bothering every forum member to be my teacher.@PeterPan_321Nov 26.2018 — #@root#1598219 Well I appreciate your help, but I assure you all arrays in all languages are not the same. In C, for example, array elements are always accessed by positional index. The kind of associative arrays I'm learning about in PHP don't exist there. And even in object oriented C++, you can't have different array elements contain completely different data types without special tricks (like having an object definition for everything, including simple numbers), and that would be considered wasteful. There are other differences, but what I've been trying to learn is the principals of associative arrays in PHP. Anyway, yes, its starting to "click".
And as far as pushing a group of temporary files into a database just so it can sort for me, I'm not saying its not a workable approach. I would consider that a wasteful for my application too, but I WILL try it as an exercise when I begin learning the PHP interface to SQL. Thanks for the aids.
@Sempervivum#1598226 I didn't think associative arrays could be indexed by position, but just checking. This was one of my reasons for believing the use of file timestamps as keys to a temporary array of files was not a good choice for my particular application. Since multiple files being received could easily have the same times stamp, using them as keys would cause files to be missed.
The method I'm using now works well, so thanks again everyone.
Confused about sorting in PHP
I have a camera motion detect system i use for watching my cats, and it FTP’s all its images to a folder in my hosting. So I cobbled together this code from examples I found, to display all the images along with the filenames and timestamps. Unfortunately the camera software insists on creating subfolders for each camera and each day, so I had to use this RecursiveIteratorIterator class to gather and display all the images. In the below, you can see where I build up 3 arrays of all the filenames, timestamps, and fullpaths for display. It works but all the photos were completely out of order. How can I modify this so that all the files are displayed sorted by time stamps. I *think
<!DOCTYPE html>
<html>
<body>
<?php
$dir_path = “private/cats/”;
$extensions_array = array(‘jpg’,’png’,’jpeg’,’JPG’,’PNG’,’JPEG’);
$total = 0;
$objects = new RecursiveIteratorIterator(
new RecursiveDirectoryIterator($dir_path),
RecursiveIteratorIterator::LEAVES_ONLY);
foreach($objects as $filepath => $object)
{
$fileinfo = pathinfo($filepath);
// skip if no extension, or extension not in my allowed list
if (!isset($fileinfo[‘extension’])) continue;
if (!in_array($fileinfo[‘extension’], $extensions_array)) continue;
$timestamps[$total] = date(“F d Y H:i:s”, filemtime($filepath));
$filenames[$total] = $fileinfo[‘filename’] . “.” . $fileinfo[‘extension’];
$filepaths[$total] = $filepath;
$total++;
}
echo “<h1>$total Image Files</h1>”;
for ($i=0; $i < $total; $i++)
{
echo “<br><hr><h1>$filenames[$i] $timestamps[$i] <br></h1>”;
echo “<img src=’$filepaths[$i]’ style=’width:100%;height:auto;’><br>”;
}
?>
</body>
</html>
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@PeterPan_321Nov 19.2018 — #Thanks guys. I have a LOT to learn about associative arrays, It didn't look like any of the sorting methods in the MANual would offer an easy fix, but that's probably because I'm just not understanding. In the meantime I came up with something that is probably an ugly kludge, but it works. In my original routine, in addition to building the three parallel arrays for the filenames, filepaths, and formatted time stamps, I added an array to hold the raw time (integer) stamps. So when that process completes, I do this... (please forgive my old school "c" mentality.)$max = max($rawTimestamps);
$newtotal=0;
for ($i=0; $i < $total; $i++)
{
$lowest = min($rawTimestamps);
if ($lowest > $max) break; // stop when no more.
for ($j= 0; $j < $total; $j++)
{
if ($rawTimestamps[$j] != $lowest) continue;
$indexes[$newtotal++] = $j; // keep index. overwrite duplicates
$rawTimestamps[$j] = $max+1; // ensure never counted again.
}}
So what i did here is I recorded the maximum value in my $rawtimestamps array and started a $newtotal variable. Then the outer loop records the lowest timestamp value in that array, while the inner loop looks for all occurrences of that timestamp, and adds the index location ($j) where they were found to a new array called $indexes. After each one is found it replaces the original integer timestamp with a value greater than the recorded max value. That prevents it from ever being discovered again as the "lowest' value. (It also makes it easy to break out of the outer loop, when the lowest value found on the last pass exceeds to original max value!).
OK, this process destroys the rawtimestamps array, but I won't ever need it again after this. The newly built up array called $indexes now serves as a map. When I next display all my files and photos, I just have one added step, to use this map value to index all my other file data...
echo "<h1>$newtotal Image Files</h1>";
for ($i=0; $i < $newtotal; $i++)
{
$ix= $indexes[$i]; // get index to progressively older files
echo "<br><hr><h1>$filenames[$ix] $timestamps[$ix] <br></h1>";
echo "<img src='$filepaths[$ix]' style='width:100%;height:auto;'><br>";
}
}
I am sure that my lack of understanding of associative arrays has made this code uglier than it needs to be. But it works, so now I have a working reference. I'll definitely try the associative array method
By the way, the editor in the new Webdeveloper.com doesn't seem to have a button to properly format code snippets, so I'm just pasting them in and hoping for the best. But is there a proper way (or some proper tags) to better format code for posts?
0
@PeterPan_321Nov 20.2018 — #In the end, as I mentioned in my long winded post (LOL), I did come up with what I'd call a brute force solution. What I was looking for was, given an array of random timestamp integers, return another array whose elements contained indexes to progressively higher (or lower) elements in the first array. Kind of a re-mapping array. Thus, if i used that new mapping array to display consecutive photos in a loop, I could use the loop counter as an index to "look up" the next (older or younger) image index in the map, for display. I thought my double loop would be inefficient, But even testing with several hundreds of photos, the processing seemed instantaneous.
I just kept thinking there might be an existing sort routine to do what I did, and there probably is. But sometimes I waste a ton of time looking for some ready made class or function to simplify a task for me, and it the end it took less time to just "roll my own". My PHP coding often still does look like old school 'c', and aside from a few different rules, its basically the same, right?
I still wish I knew the proper way to post code on this board.
0
@cootheadNov 20.2018 — #>@PeterPan_321#1598006
**[color=#069] **
I still wish I knew the proper way to post code on this board.[/color]
This has been answered here...
_coothead_
0
@PeterPan_321Nov 20.2018 — #0
@PeterPan_321Nov 20.2018 — #Thanks again!
0
@PeterPan_321Nov 21.2018 — #Would you be so kind as to give me an example, based on the problem I just solved via a different route? It will take some explaining so bear with me. I started with a two simple one dimensional arrays. One of filepaths to various image files, the other to unix time stamps for these same files. So a given index (let's say $i) could be used to look up the file path and timestamp.
Now, since I wanted to display the images in order of their ascending timestamps, I wrote the double loop I described earlier to create another simple array called $indexes, My "sort" routine progressively stored the index location to progressively older timestamps. So now, when I went to display the images, instead of just using a for() loop to progressively display the time stamps and images, I could take my index variable $i, and use it to "look up" the next index to be displayed in my "map" array...
$correctedIndex = $indexes($i);
So now, even though $i simply incremented from 0 to the total, my $correctedindex would ensure that the timestamp and image I pulled from the original arrays were in time-wise order.
So now, lets go back to that array i created with my sort routine. Again, it was a simple one dimensional array, filled with timestamps in random order. If I simply sorted that array, I would lose all the original index references I needed. But, maybe if if I had an associative array, where the integer timestamps were 'associated' with the filepath of each image, THEN if I sorted by the timestamps, I'd be able to do a "forEach" construct, and know that the timestamps and filepaths would be accessed in the order of the sort.
But all that is a concept in my head, and I've not been able to figure out how to implement it based on the online MANual for PHP associative arrays.
0
@PeterPan_321Nov 21.2018 — #Thanks 0
@NogDogNov 21.2018 — #In some languages, you have arrays and hashes, where the "keys" in arrays are always integers (i.e. "indexes"), while hashes only have string keys. In PHP, there are only arrays, and they can use both string and integer keys interchangeably. Each of these is valid, though the "confusing_mess" is generally to be avoided (example in command line mode, thus those php >[code=php]
14:25 $ php -a
Interactive shell
php > $my_array = array('one', 'two');
php > $my_array[] = 'threeeee';
php > var_export($my_array);
array (
0 => 'one',
1 => 'two',
2 => 'threeeee',
)
php > $my_array[2] = 'three';
php > var_export($my_array);
array (
0 => 'one',
1 => 'two',
2 => 'three',
)
php > $my_associative_array = array('first' => 'one', 'second' => 'two', 'third' => 'three');
php > var_export($my_associative_array);
array (
'first' => 'one',
'second' => 'two',
'third' => 'three',
)
php > $my_confusing_mess = array('one', 'second' => 'two', 'three');
php > var_export($my_confusing_mess);
array (
0 => 'one',
'second' => 'two',
1 => 'three',
)
php >
[/code]0
@PeterPan_321Nov 21.2018 — #So if I understand the above correctly...
1) the raw unix file time integer is the first item in the $fi array, which becomes the key.
2) I can then add several more items and use => symbols to 'associate' the given name (like "filename") with each subsequent item
3) as long as the key (raw timestamp) is unique, I can continue adding additional files this way.
If that is correct, some more questions...
1) what would I do now to "sort" the whole associated array now, by those keys?
2) Can this type of array still be indexed? such as for($i =0; i < count($fi); $i++) { do stuff}?, and would the returned array elements now be in order of the sorted keys?
3) within the loop, I could then access my elements as $fi[$i] => "filename" ? and have them accessed in timestamp sorted order?
4) and finally, an unrelated but possibly troublesome question. Wouldn't using the timestamp as a key mean multiple files with the same timestamp would get overwritten? If so, I'm thinking it might be better if a simple increment number was used as the key ($number++), and then add the raw timestamp integer as an associated element. I could still sort based on the "timestamp" element I choose, right? I understand the order of identical timestamps is undefined in a sort, as long as files aren't lost in the process.
0
@PeterPan_321Nov 23.2018 — #One thing I still believe will be a flaw here. If I move to associative arrays for this little project and let timestamps be my keys, multiple images that have the same timestamp will be lost. Therefore, in addition to timestamps and filepaths I will have to add another item $count, that simply increments ($count++) and let that be the key since it will always be unique. So then I will have to figure out how to do my sort (or multisort) based on the key, but on on the 'timestamp' element rather than the key. Is that possible?
0
@PeterPan_321Nov 24.2018 — #>@root#1598207 Ireally don't think you fully understand arrays.
Well I confess you're right. But to be fair I've used arrays all my life and have been coding for many years, and have a level of proficiency in other languages. Its the properties of PHP arrays that have me confused. Part of the problem is that everyone that does fully understand are not always the best teachers, and the MANual for this language, though a good reference, is not the best teacher for learning the language from the ground up.
>
> KEYS are the ASSOCIATIVE array element, NUMERIC arrays are in their own right an associative array as the array position = the key, the value of the element is that property associated with the key.
>
> time() = 12345566789
I don't understand that syntax. I would take that as a function named time() is being set equal to a number.
>
> So its NUMERIC compared to "2018-10-21T12:34:56.789"
I understand the difference between a number and a string. But ordinary arrays referenced by position rather than key could also be an array of strings or other any objects. I don't think you're inferring that an array containing strings MUST be associative. Are you saying that arrays referenced by position could also be referenced by association?
>
> of should I put it in a format that you might recognise...
>
> $arrayData = array( 123456789 => "something happened",
> 123499876 => "something else happened",
> 123698789 => "and something else happened");
I've seen that use of => for an associative array. So USING that syntax lets the compiler or interpreter know that you're intention is to use this array as an associative array?
Here's a yes/no question: can an associative array also be referenced by position? For the above, could array position 0 (or $arraydata[0] ) be used to reference the key 123456789 and the string "something happened? in a for() loop with positional indexes?
> and the PHP time() function outputs an integer number that is UNIQUE!!!
But how does that relate to my MY situation? I was dealing with the timestamps on files which only resolve to a second, so its possible for several files being continually uploaded to end up with identical timestamps. hence, I realized I could not use that timestamp as a key, because multiple files stored in the array using the same key reference would overwrite each other.
I'm beginning to understand, but few manuals these days (including the PHP MANual) is not written as well as the Kernighan and Ritchie C manual. What I need, really, is a good complete reference and teaching book like that. I can usually get enough from MANual and other examples via GOOGLE. But if I really want to master these concepts, such a complete reference would be better than bothering every forum member to be my teacher.
0
@PeterPan_321Nov 26.2018 — #And as far as pushing a group of temporary files into a database just so it can sort for me, I'm not saying its not a workable approach. I would consider that a wasteful for my application too, but I WILL try it as an exercise when I begin learning the PHP interface to SQL. Thanks for the aids.
The method I'm using now works well, so thanks again everyone.