I have been trying to analyze it for like hours now but I can't understand what was wrong with my code :(
$d = 1; //I declare this variable as 1
$a = 0;
while($d<$arraycount-2){
while ($a < 40){
$c = 0;
$b = 0;
while($c < $fc){
$finaloutput = $finaloutput.$database_returned_data[$d][$c].","; //But here, in this loop $d is always 1
$c++;
}
while($b < 5){
$finaloutput = $finaloutput.$mydata[$a][$b].",";
$b++;
}
$finaloutput = $finaloutput."--END--";
$a++;
}
$d++; //But it increments successfully. Hence, the while loop terminates after it meets the criteria.
}
The variable $d is always 1 inside the other loop but it increments outside the loop. Note there is a while statement inside the while. Is there anything wrong?
I'm using $d for my array:
$finaloutput = $finaloutput.$database_returned_data[$d][$c].",";
I am a noob poster. Feel free to ask for more details :)
You don't set $a here:
while($d<$arraycount-2){
while ($a < 40){
So on every iteration besides the first this while condition won't run.
just change it to:
while($d<$arraycount-2){
$a = 0;
while ($a < 40){
Related
I am solving this not understandable script, I even don't know where from to start. Maybe someone will help me.
I got two arrays example:
$a1 = array(1,2,3 ...);
$a2 = array(4,5,6 ...);
what I need is that first array will divide all values by itsel
for this I would like to get script which will work like this (array values can be savet to the same name because will be anyway continue with them, can be new variable, in this example I use new). In the same way variable can be devidet by itself to get 1 but prefer not to. Example of count.
$b1 = array([0]/[1], [0]/[2], [0]/[3], [1]/[0], [1]/[2], [1]/[3], [2]/[0], [2]/[1], [2]/[3], [3]/[0], [3]/[1], [3]/[2]);
$b2 = array( *** The same like $b1 ***);
On the end will go foreach to write values to table, this I solved already
echo "<table><tr>";
foreach($b1 as $key1 => $val1){
foreach($b2 as $key2 =>$val2){
echo "<td>".$key1.$key2."<br/>".val1*val2."</td>";
}
echo "</tr><tr>";
}
echo "</tr></table>"
Anyone can give me a help to this issue?
To do the division of each element is relatively simple. You do it with 2 for loops. The one thing you have to bear in mind, however, is avoiding division by 0. Do you have elements that could be 0? If so, do you want the division result to be 0, or the same as the numerator? the code I show below assumes the latter:
function getDivided($array) {
$length = count($array);
$return = [];
for ($i = 0; $i < $length; $i++) {
for ($j = 0; $j < $length; $j++) {
if ($i === $j) continue;
//the following assumes that the values in the array are never < 1 Change this according to your needs
$return[] = $array[$i] / max($array[$j], 1);
//Another option is to use a conditional
$return[] = $array[$j] === 0 ? $array[$i] : $array[$i] / $array[$j];
}
}
return $return;
}
$b1 = getDivided($a1);
$b2 = getDivided($a2);
I've had this problem a few times now when for looping over an array item.
In this instance I'm generating all 2 letter combinations of the alphabet.
The code works (and I know there's a much easier way of doing it with 2 for loops, but I'm trying something different).
However I have to do count -1 as count() returns the number 26 for the array length, however the 26th item obviously doesn't exist as it's 0 based?
Is there not a version of count() that works on a zero-based basis?
<?php
$alphas = range('a', 'z');
$alphacount = count($alphas);
// Why do I have to do this bit here?
$alphaminus = $alphacount -1;
$a = 0;
for ($i=0;$i<$alphacount;$i++) {
$first = $alphas[$a];
$second = $alphas[$i];
if ($i === $alphaminus && $a < $alphaminus ) {
$i = 0;
$a ++;
}
echo "$first$second<br>";
}
?>
Without $alphaminus = $alphacount -1; I get undefined offset 26?
How about:
<?php
$alphas = range('a', 'z');
$alphacount = count($alphas);
$a = 0;
for ($i=0;$i<$alphacount;$i++) {
$first = $alphas[$a];
$second = $alphas[$i];
if ($i >= $alphacount && $a < $alphaminus ) {
$i = 0;
$a ++;
}
echo "$first$second<br>";
}
So you don't have to to -1 since you don't like it! :)
And how about:
$alphas = range('a', 'z');
for ($i = 0; $i < count($alphas); $i++) {
for ($a = 0; $a < count($alphas); $a++) {
echo "{$alphas[$i]}{$alphas[$a]}\n";
}
}
Or forget about arrays! This is more fun :)
array_walk($alphas, function ($a) use ($alphas) {
array_walk($alphas, function ($b) use ($a) {
print "$a$b\n";
});
});
The problem is that you reset $i to 0 in the loop; then on encountering the end of the loop $i is incremented, so the next run in the loop will be with $i = 1 instead of $i = 0.
That is, the next subrange of letters starts with (letter)b instead of (letter)a. (See your output: the next line after az is bb rather than ba.)
Solution: reset $i to -1 in the loop, then at the end it will run with the value 0 again.
You have 26 characters, but arrays in PHP are indexed from 0. So, indexes are 0, 1, ... 25.
count is 1-based and arrays created by range() are 0-based.
It means that:
$alphas[0] == a
$alphas[25] == z
$count($alphas) = 26; // there are 26 elements. First element is $alphas[0]
Why does it have to be so complicated? You could simply do
foreach ($alphas as $alpha)
{
foreach($alphas as $alpha2)
{
echo $alpha.$alpha2."<br>";
}
}
Note: It is mostly not a good idea to manipulate the loop counter variable inside the body of that very loop. You set $i to 0 on a certain condition. That could give you unexpected results, hence the reason why you have to navigate around it.
When I want to iterate an array I usually do:
foreach ($array as $a)
{
//do something with $a
}
I just want to know if is possible do something like this with a for loop:
for ($i = 0; $i < count($array); $a = $array[$i]; $i ++)
{
//do something with $a
}
Edit: When I test the code above, the for syntax is not valid.
skip the $a = $array[$i] part of the for-loop (This is assigned INSIDE of the loop and not in the declaration of the loop)
You should do like this instead:
for ($i = 0; $i < count($array); $i ++)
{
$a = $array[$i]; //Gets value of element in array $array
//Do something with it...
}
You say you want control of the element of an array.
You can do the equalivalent by doing like this (adding a key-value to the foreach-loop)
foreach ($array as $key=>$i)
{
$a = $i[$key];
}
Replace the third semicolon with a comma. It's not the entire solution (assignment is done too late), but it should explain sufficiently how a for statement works.
The for loop doesn't need to handle the $a = $array[$i]; as part of its arguments.
You can just move it to the body of the loop, something like this:
for ($i = 0; $i < count($array); $i++){
$a = $array[$i];
//do something with $a
}
for ($i = 0; $i < count($array); $i ++){
$a = $array[$i];
}
The for loop definition takes three statements you provided four. Move the assignment of $a into the actual loop.
I have 2 arrays, both are multidimensional with same number of elements and same values, which are on different positions (those values are actually ID-s from my database, so one ID appears only once). How can I sort second array with values which are in first array?
For example - if first array looks like:
$array1[0][0] = 1;
$array1[0][x] = it doesn't matter what's here
$array1[1][0] = 4;
$array1[1][x] = it doesn't matter what's here
$array1[2][0] = 3;
$array1[2][x] = it doesn't matter what's here
...
how to sort second array so it would have same values as array1 on indexes [0][0], [1][0], [2][0], etc.
How I could solve problem is:
$i=0
while ($i < (count($array1)-2)){ // * check down
$find_id = $array1[$i][0];
// here I need to search for index of that ID in other array
$position = give_index($find_id, $array2);
// swapping positions
$temp = array2[$i][0];
$array2[$i][0] = $array2[$position][0];
$array2[$position][0] = $temp;
// increasing counter
i++;
}
function give_index($needle, $haystack){
for ($j = 0, $l = count($haystack); $j < $l; ++$j) {
if (in_array($needle, $haystack[$j][0])) return $j;
}
return false;
}
*There is only -2 because indexes start from 0 and also for the last element you don't need to check since it would be automatically sorted by last iteration of while-loop.
I don't find this solution good as I think that this is quite simple issue (maybe it's not even correct). Is there easier way in PHP that I'm missing?
This is the most efficient way I can think of:
function swap(&$a, &$b) {
$t = $a;
$a = $b;
$b = $t;
}
function find_index($id, $array, $from = 0) {
$index = false;
for ($i = $from, $c = count($array); $i < $c; $i++) {
if ($array[$i][0] == $id) {
$index = $i;
break;
}
}
return $index;
}
for ($i = 0, $c = count($array1); $i < ($c - 2); $i++) {
if ($array1[$i][0] != $array2[$i][0]) {
$fi = find_index($array1[$i][0], $array2, $i);
swap($array2[$i][0], $array2[$fi][0]);
}
}
What changes from yours?
I've defined a swap() function in order to swap any variable. That doesn't cost anything and makes everything look nicer. Also you can reuse that function later if you need to.
In the find_index (give_index in your code) we stop the loop once we find the correct index. Also we avoid the cost of an in_array function call.
We modified the find_index function to start only from the part of the array we haven't checked yet. Leading to a way more efficient way of scan the array.
In the for loop (a while loop was just wrong there) we stored the count of the array once, avoiding multiple calls.
Also we swap the $array2 values only if they are in the wrong place.
Other improvements
If you know anything else of the $array2 array you can make this even more performant. For example if you know that indexes are alternated like in $array1 you can change the main for loop from:
for ($i = 0, $c = count($array1); $i < ($c - 2); $i++) {
to
for ($i = 0, $c = count($array1); $i < ($c - 2); $i+2) {
(notice the $i+2 at the end) And you could do that in the find_index function as well.
Look into usort (http://php.net/manual/en/function.usort.php).
It provides a simple way to sort arrays using a user provided comparison function.
I have been working with the same loop for a couple days now, and it still won't work the way I want it to. I have tried both for, foreach and while and it still refuses to work.
The code that won't work is simply:
if(!empty($_POST['submit'])){
$d = count($_POST['deleteT']);
for ($pi = 1; $pi <= $d; $pi++) {
echo "Banned ".$_POST['deleteT'][$pi]."</br>";
}
}
If deleteT has two values: 'Bob' and 'Joe' it will print:
Banned Joe
Banned
Does anyone have any insight into why this is going on?
Start your loop index with $pi = 0; and only loop while $pi < $d.
I think one of your problems is in your count statement, then with the <= condition in the for loop.
If you use count(), then just use <. Example:
$c = count($my_array);
for ($i = 0; $i < $c; $i++) {
// do stuff
}
That said, an easier way to iterate over an array is with foreach. Like this:
foreach ($my_array as $key => $val) {
// do stuff with $val or $key
}