I want to increment the int on the end of my string which together makes up the complete value.
$btnid = 'btnid1';
for($i = 1; $i < $countP; $i++) {
$btnid = 'btnid' . ++;
}
I tried different types of concatenation but I can't seem to get it to work if I just set it to 1 it works but I need the string there too.
Just append $i to the string btnid in each loop iteration.
$string = 'btnid';
for($i = 1; $i < $countP; $i++) {
$btnid = $string . $i;
}
As a side note (and seriously, DO NOT actually do this) so long as you don't go past btnid9, you can just increment the string.
$btnid = 'btnid1';
for($i = 1; $i < 9; $i++) {
$btnid++;
}
echo $btnid; // btnid9
If you go over, things get a bit weird:
$btnid++;
echo $btnid; // btnie0
Manual page: http://php.net/manual/en/language.operators.increment.php
Related
I have the PHP code below:
<?php
$length = $_GET["length"];
$maxValue = $_GET["maxValue"];
$distribution = array();
for($j = 0; $j < $maxValue; $j++) {
$distribution[j] = 5;
}
$x = 0;
$x++;
for($j = 0; $j < $maxValue; $j++) {
echo $distribution[j] , " ";
}
echo $x;
?>
$x starts as 0 and is incremented by 1. However, just below $x is incremented, I am also incrementing the first element of the "distribution" array - $distribution[0]. And it's not working. It worked fine when I was initializing the elements (set them to 5).
Any ideas on why it might now be working? I am probably referencing the array element wrong. But this seems inconsistent.
When you say $distribution[j] -> php doesn't understand the j as a variable - but rather as an undefined constant
It looks like you are trying to say $distribution[$j] - which is partially -why your increments aren't working - -
The other reason would be that you aren't ever calling $distribution[$j]++ --- so there is no incrementation happening...
I'm looking to increment a number after a certain letter.
I have a list of own Ids and i would like to increment it without write it manually each time i add a new id.
$ids = array('303.L1', '303.L2', '303.L3', '303.L4');
so i use the END() function to extract the last id from this array.
this is what i've tried but i cannot get a result.
$i = 0;
while($i <= count($ids)){
$i++;
$new_increment_id = 1;
$final_increment = end($last_id) + $new_increment_id;
}
echo $final_increment;
New method, but it is adding me double dot between number and letter.
$i = 0;
while($i <= count($ids)){
$i++;
$chars = preg_split("/[0-9]+/", end($ids));
$nums = preg_split("/[a-zA-Z]+/", end($ids));
$increment = $nums[1] + 1;
$final_increment = $nums[0].$chars[1].$increment;
}
//i will use this id to be inserted to database as id:
echo $final_increment;
Is there another way to increment the last number after L ?
Any help is appreciated.
If you don't want a predefined list, but you want a defined number of ids returned in an $ids variable u can use the following code
<?php
$i = 0;
$number_of_ids = 4;
$id_prefix = "303.L";
$ids = array();
while($i < $number_of_ids){
$ids[] = $id_prefix . (++$i); // adds prefix and number to array ids.
}
var_dump($ids);
// will output '303.L1', '303.L2', '303.L3', '303.L4'
?>
I'm a bit confused because you say "without write it manually". But I think I have a solution:
$ids = array('303.L1', '303.L2', '303.L3', '303.L4');
$i = 0;
while($i <= count($ids)){
++$i;
//Adding a new item to that array
$ids[] = "303.L" . $i;
}
This would increment just that LAST number, starting at zero. If you wanted to continue where you left off, that'd be simple too. Just take $i = 0; and replace with:
//Grab last item in array
$current_index = $ids[count($ids) - 1];
//Separates the string (i.e. '303.L1') into an array of ['303', '1']
$exploded_id = explode('.L', $current_index);
//Then we just grab the second item in the array (index 1)
$i = $exploded_id[1];
I am having some problems with PHP.
I used while to sum a number's digits always that it has more than two digits, some how, it gets into an infinity loop.
e.g: 56 = 5 + 6 = 11 = 1+1= 2.
Here is the code:
$somaP = 0;
$numPer = (string)$numPer; //$numPer = number calculated previously
while (strlen($numPer) > 1){
for ($j = 0; $j < strlen($numPer); $j++){
$somaP = $somaP + (int)($numPer[$j]);
}
$numPer = (string) $somaP;
}
Can anyone help me? Guess it is a simple mistake, but I couldn't fix it.
You need to reset the value of $somaP in your while loop.
Currently it continues to increase its value every time through the loop.
Try this:
$numPer = (string)$numPer; //$numPer = number calculated previously
while (strlen($numPer) > 1){
$somaP = 0;
for ($j = 0; $j < strlen($numPer); $j++){
$somaP = $somaP + (int)($numPer[$j]);
}
$numPer = (string) $somaP;
}
Take a look at this line:
$numPer = (string) $somaP;
It seems that the length of $somaP is never lesser (or equal) than 1. So the length of $numPer is never lesser (or equal) than 1.
What are you trying to do?
It's unclear to me.
This for example would add every number in a string together?
E.g "1234" = 1+2+3+4 = 10
$total = 0;
for($i = 0; i < strlen($string); $i++){
$total += $string[$i];
}
echo $total;
This looks cleaner I would say:
$numPer = 56;
while ($numPer > 9){
$numPer = array_sum(str_split($numPer));
}
echo $numPer;
PHP handles all string <> number conversions for you, so no need to do (string) on a number unless really needed.
How are they different? Here's what I'm thinking, but I'm not sure....
If you use pre-incrementation, for example in a for loop with ++j, then you are basically saying: "Make a copy of the value of j for use in the loop, then increment j, then go through the statements in the loop with the copy of j." If you are using post-incrementation in the same loop j++, then you are basically saying: "Make a copy of the value of j for use in the loop, then go through the statements in the loop with the copy of j, then increment j."
The reason I'm unsure is because I've created a for loop that multiplies the value of j by 10 and then outputs the result for j=1 through j=12, using both post- and pre-incrementation. The human readable output is exactly the same with post- and pre-incrementation. I'm thinking, 'How are the outputs exactly the same if there isn't some kind of copy operation involved?'
So, I'm guessing the difference between pre- and post-incrementation truly becomes important, in php, when I use references (which act as pointers in php) rather than names for return values? This would be because copies of references aren't made, so pre-incrementation would be: "Increment j, then go through the statements in the loop with the changed value of j, then increment j again...," whereas post-incremetation would look like: "Use the value of j for the statements in the loop, then change the value of j, then go through the loop with the new value of j..."
Pre- or post-incrementing do not magically delay things until later. It's simply inline shorthand.
// pre-increment
$var = 5;
print(++$var); // increments first, then passes value (now 6) to print()
// post-increment
$var = 5;
print($var++); // passes value (still 5) to print(), then increments
Now let's look at a loop.
for ($i = 0; $i < 9; $i++) {
print($i);
}
The last part of the loop declaration (the $i++) is simply the statement to execute after each time through the loop. It "passes" the value to nowhere, then increments it. $i isn't used anywhere at that time. Later when the next statement is executed (print($i);), the value of $i has already increased.
// add 1, then do nothing with $i
for ($i = 0; $i < 9; ++$i) {}
// do nothing with $i, then add 1
for ($i = 0; $i < 9; $i++) {}
Whichever way you do it, $i will be the same within the loop.
If it helps, you can think of them as small routines that kind of do this:
// ++$i
{
$i = $i + 1;
return $i;
}
// $i++
{
return $i;
$i = $i + 1;
}
As I reread your question, I think the confusion is more with how the loop works than how increment operators work. Keeping in mind that the increment is a straightforward, all-at-once operation, here's how third expression in the loop works.
// here's a basic loop
for ($i = 0; $i < 9; $i++) {
// do loop stuff
print($i);
}
// this is exactly what happens
for ($i = 0; $i < 9; ) {
// do loop stuff
print($i);
$i++;
}
Just because that last line can be put in the loop declaration doesn't give it any special powers. There are no references or anything used behind the scenes. The same $i variable is seen both inside and outside the loop. Every statement inside or outside the loop directly looks up the value of $i when necessary. That's it. No funny business.
When doing $x++, you are post-incrementing... This means that the incrementation will only occur after the statement has been evaluated.
So, given the following code:
$x = 10; $y = 0; $z = 5;
$y = $z * $x++;
PHP does this:
$x = 10; $y = 0; $z = 5;
$y = $z * $x++;
// Ignore Post-Increment, Evalutate
$y = $z * $x;
$y = 5 * 10;
// Now Increment x - POST-INCREMENT
$x = $x + 1;
$x = 10 + 1;
$x = 11;
// Continue evaluating statement
$y = 5 * 10;
$y = 50;
When doing ++$x, you are pre-incrementing... This means that the incrementation will occur before the statement is evaluated:
$x = 10; $y = 0; $z = 5;
$y = $z * ++$x;
// Do Pre-Increment
$x = $x + 1;
$x = 10 + 1;
$x = 11;
// Evaluate
$y = $z * $x;
$y = 5 * 11;
$y = 55;
In the case of a for loop in PHP, PHP evaluates a for loop as follows:
for($i = 0; $i < 30; $i++) {
doSomething();
}
// Is evaluated EXACTLY as such by PHP
$i = 0;
while($i < 30) {
doSomething();
$i++;
}
The first expression ($i = 0) is evaluated (executed) once unconditionally at the beginning of the loop.
In the beginning of each iteration, $i < 30 is evaluated. If it evaluates to TRUE, the loop continues and the nested statement(s) are executed. If it evaluates to FALSE, the execution of the loop ends.
At the end of each iteration, $i++ is evaluated (executed) as an independent expression.
Therefore, post-incrementing or pre-incrementing a variable as the third expression in the loop doesn't have an effect on the behavior of it. In this simple case, both expressions will behave exactly the same.
However, in a complex loop such as the following:
for($i = $j = 0; $i < 30; $i += ++$j) {
$j = getResult($j);
}
Post-incrementing or pre-incrementing $j directly affects the value of $i according to the examples above. In this case, you need to choose exactly what you want to do.
$i = 0;
echo $i++;
echo $i;
$j=0;
echo ++$j;
echo $j;
Pre increment display incremented value. But Post increment display value then increment. About code will output 01 and 11
I have a problem where I have an array $user.
I have $_SESSION['players'] which has the total amount of $user.
I need a function where I can take the user1 and 2 and use them. Then move on to user3 and 4 and use them, and so on.. until I have used all the players. Obviously the total $user[$i] would be players-1.
Anyone have a solution for this?
Thanks
Would this suit your needs? This requires that there be an even number of players to work properly though, unless you stick in a check for odd numbers:
for ($i = 0; $i < $_SESSION['players']; $i += 2) {
$userA = $user[$i];
$userB = $user[$i + 1];
// Do things with $userA and $userB variables...
}
just because you're taught how to use for loops in one way does not mean that you're stuck continuing to use them the way you were taught:
$length = count($users);
$length = $_SESSION['players'];
for ($i = 0; $i < $length; $i += 2)
{
if (!isset($user[$i], $user[$i + 1])) break;
$userOne = $user[$i];
$userTwo = $user[$i+1];
//do stuff
}
I realized that isset wasn't necessary, the for call could be modified more:
$length = $_SESSION['players'];
for ($i = 0; ($i + 1) < $length; $i += 2)
{
$userOne = $user[$i];
$userTwo = $user[$i+1];
//do stuff
}
EDIT to change how the length was calculated:
EDIT to validate that user exists
EDIT to add consolidated version