Recently, my exams got over. My last exam was based on PHP. I got the following question for my exam:
"Convert the following script using for loop without affecting the output:-"
<?php
//Convert into for loop
$x = 0;
$count = 10;
do
{
echo ($count. "<BR>");
$count = $count - 2;
$x = $x + $count;
}
while($count < 1)
echo ($x);
?>
Please help me as my computer sir is out of station and I am really puzzled by it.
Well, If I understand well, You have to use "for" loop, instead of "do...while", but the printed text must not change.
Try:
$count = 10;
$x = 0;
$firstRun = true;
for(; $count > 1 || $firstRun;) {
$firstRun = false;
echo ($count . "<BR>");
$count -= 2;
$x = $x + $count;
}
echo ($x);
By the way loop is unnecessary, because $count will be greater than 1 after the first loop, so the while will get false.
EDIT
$firstRun to avoid infiniteLoop
$count in loop
EDIT
Fixed code for new requirement
Removed unnecessary code
Hmmm I don't know if your teacher wanted to own you... but the do{} will execute only once since $count is never < 1.
The output of your teacher's code is:
10
8
I presume there was a mistake in the code and the while would be while($count > 1) which would make more sense (since it's weird to ask for a loop to output only 10 8) and would result in this output:
10
8
6
4
2
20
Then a good for() loop would have been :
$x = 0;
$count = 10;
for($i = $count; $i > 1; $i -= 2)
{
$count -= 2;
echo $i . "<br>";
$x += $count;
}
echo $x;
Which will output the same values.
If you can, ask your teacher for this, and comment the answer ^^ ahahah
Related
I need to find the averege after using a loop counting ever 3rd to a 100. The loop part is easy enough, but I need to sum every value then divide the sum on the total of values.
for ($x = 3; $x < 100; $x+=3) {
echo $x.", ";
}
This is the loop I need to use. How to I sum the values this produces and how do I find how many values this loop produces?
I believe the intention here is to learn about loops, otherwise this stuff can be done without looping too.
For learning purpose, you can simply introduce two variables count and sum and compute them inside the loop. For count, you just increment it on each iteration. For sum, you add the current value of x into sum. After the loop you print both variables.
$count = 0;
$sum = 0;
for ($x = 3; $x < 100; $x+=3) {
echo $x.", ";
$count++;
$sum+=$x;
}
echo $sum;
echo $count;
add your elements into an array and then use array_sum to sum the array elements , then divide the sum by the count of your array
$arr = [];
for ($x = 3; $x < 100; $x+=3) {
// echo $x.", \n";
$arr[] = $x;
}
print_r(array_sum($arr) / count($arr));
// Output : 51
$i=0;
$tempx=0;
for ($x = 3; $x < 100; $x+=3) {
//total sum
$tempx = $tempx + $x;
//count of how many times the loop ran in this case 33 times
$i++;
}
//first $i was 0 so we add 1
$i=$i + 1;
//getting the average
$average=$tempx / $i;
echo $average;
//output
For the last answer i think we should not do:
//first $i was 0 so we add 1 $i=$i + 1;
Regards
I need to make a loop in php that says 1*9 = 9 2*9 = 18 and 1*8 = 8 and 1*7 = 7 etc in loop so the result will be this:
1*7 = 7
2*7 = 14
3*7 = 21
1*8 = 8
2*8 = 16
3*8 = 24
1*9 = 9
2*9 = 18
3*9 = 27
And I need to use a nested loop for that i tried some things out but i cant get it to work here is what is did. But for the most part i don't really understand what nested loops do and what there used for. hope you can help me thanks!
for ($tafel7 = 0; $tafel7 <= 9; $tafel7++) {
for($tafel7 = 0; $tafel7 <= 9; $tafel7++){
for($tafel7 = 0; $tafel7 <= 9; $tafel7++){
$antwoord9 = $tafel7 * 9;
echo "$tafel7 x 8 = $antwoord9 <br>";
$antwoord8 = $tafel7 * 8;
echo "$tafel7 x 8 = $antwoord8 <br>";
$antwoord7 = $tafel7 * 7;
echo "$tafel7 x 7 = $antwoord7 <br>";
};
};
};
Your question is not as clear but if you just want the exact result, here's the code:
for($i = 7; $i <= 9; $i++){
for($j = 1; $j <= 3; $j++){
$result = $i * $j;
echo $j." * ".$i." = ".$result."<br>";
}
}
If you need to print complete tables, then try this:
for($i = 1; $i <= 9; $i++){
for($j = 1; $j <= 10; $j++){
$result = $i * $j;
echo $i." * ".$j." = ".$result."<br>";
}
}
As far as the explanation is concerned, then listen:
A normal loop works by executing a block of statement(s) again and again until a condition is met.
So, nested loops are basically loops in another loop. This means that the block of code will be executed 'n' number of times by the inner loop, and then the inner loop will again be executed by the outer loop, again 'n' number of times.
'n' means whatever the number of times the conditions are met for the respective for loops.
Hope you got my explanation!
You need to loop over your two variables, (1) the left operand and (2) the right operand
for ($right = 7; $right <= 9; $right++) {
for ($left = 1; $left <= 3; $left++) {
$product = $left * $right;
echo "{$left} x {$right} = {$product} <br>";
}
}
In this example, I have to loops one with the times table you want eg 7, 8 and 9 "tafel" and the other one with how many times you want it to run for each times table "$hoeveel". This can easily be altered to more times tables or how many times you want to run, you also only need to export the values once as it cycles through the loops anyways. Hope it helps.
for ($tafel = 7; $tafel <= 9; $tafel++) {
for ($hoeveel = 1; $hoeveel <= 3; $hoeveel++) {
$antwoord = $tafel * $hoeveel;
echo "$tafel x $hoeveel = $antwoord <br>";
}
}
I am revisiting PHP and want to relearn where i lack and i found one problem, i am unable to understand the following code, where as it should output 6 according to the quiz, i got it from but i broke it down to simple pieces and commented out to better understand, according to me the value of $sum should be 4, but what i am doing wrong, maybe my breakdown is wrong?
$numbers = array(1,2,3,4);
$total = count($numbers);
//$total = 4
$sum = 0;
$output = "";
$i = 0;
foreach($numbers as $number) {
$i = $i + 1;
//0+1 = 1
//0+2 = 2
//0+3 = 3
//0+4 = 4
if ($i < $total) {
$sum = $sum + $number;
//1st time loop = 0 < 4 false
//2nd time loop = 0 < 1 false
//3rd time loop = 0 < 2 false
//5th time loop = 0 < 3 false
//6th time loop = 4 = 4 true
//$sum + $number
//0 + 4
//4
}
}
echo $sum;
This is very basic question and might get down vote but it is also a strong backbone for people who want to become PHP developer.
You don't understand the last part in the loop. It actually goes like this now:
if($i < $total) {
$sum = $sum + $number;
//1st time loop: $sum is 0. $sum + 1 = 1. $sum is now 1.
//2nd time loop: $sum is 1. $sum + 2 = 3. $sum is now 3.
//3rd time loop: $sum is 3. $sum + 3 = 6. $sum is now 6.
//4th time loop: it doesn't get here. $i (4) < $total (4)
//This is false, so it doesn't execute this block.
}
echo $sum; // Output: 6
I altered your script a little so that it will print out what it's doing as it goes. I find it useful to do this kind of thing if I'm having a hard time thinking through a problem.
$numbers = array(1,2,3,4);
$total = count($numbers);
$sum = 0;
$i = 0;
$j = 0;
foreach($numbers as $number) {
$i = $i + 1;
echo "Iteration $j: \$i +1 is $i, \$sum is $sum, \$number is $number";
if ($i < $total) {
$sum = $sum + $number;
echo ", \$i is less than \$total ($total), so \$sum + \$number is: $sum";
} else {
echo ", \$i is not less than \$total ($total), so \$sum will not be increased.";
}
echo '<br>'; // or a new line if it's CLI
$j++;
}
echo $sum;
Lets Explain
Your initial value of $i is 0 but when you start looping you increment it by 1, so the start value of $i is 1.
When checking the condition you did't use equal sign to check for the last value whether you start value is 1. So its clear that your loop must be run for 1 less of total.
$i = 0;
foreach($numbers as $number) {
$i += 1;
if ($i < $total)
$sum += $number;
}
echo $sum;
Analysis
Step: 1 / 4
The value of $number is: 1 And The value of $i is: 1
Step: 2 / 4
The value of $number is: 2 And The value of $i is: 2
Step: 3 / 4
The value of $number is: 3 And The value of $i is: 3
When the loop again go for a check the value of $i increased by 1 and at 4. So trying to match the condition if ($i < $total), where the value of $i and $total is equal, so it will return false. So the loop only run for 3 time.
Result
6
So I have a query, and though my query can possibly return 20 results, I only want it to show the first 9 results. There is a dumb reason I'm not just limiting the query results to 9, for this purpose I need to know how to stop the while function if $i reaches 9.
Code is
$i = 0;
while($array = mysql_fetch_array($queryresults) && $i <= '9')
{
echo $array['id'];
$i++;
}
How do I get it to stop putting out more echoes after 9th result? Thank you!
Putting the limiting condition first will also make sure you only fetch 9 rows, not and 10 and one discard because && is called lazy (if the first part is false, it wont even look at the next part).
$i = 0;
while($i < 9 && $array = mysql_fetch_array($queryresults)){
echo $array['id'];
$i += 1;
}
or if you want to be fancy:
$i = 9;
while($i-- > 0 && $array = mysql_fetch_array($queryresults)){
echo $array['id'];
}
But I find this error prone ..
$i = 0;
while($array = mysql_fetch_array($queryresults) && $i++ < 9)
echo $array['id'];
}
Notes:
No need to put 9 in quotes
You can increment-after-compare by doing $i++ in the while loop condition (although you don't have to, you could also put it after echo $array['id'] in the while loop body).
Careful! You want < 9 and not <= 9 since starting at zero, or you'll get 10 iterations of the loop.
Cheers
Your $i++ needs to be inside the while loop
You should also have $i <= 9 instead of $i <= '9' but it should still work as is
'9' needs to be 9
$i = 0;
while($array = mysql_fetch_array($queryresults) && $i < 9){
echo $array['id'];
$i += 1;
}
hello i'm beginner for programming I've got a homework. googled it but couldnt find anything...
i need to get the total value of numbers from 1 to 10. this need to be done in loop. but couldn't figure which loop should i use. if you can also give me an example code thats would be great.
This is a homework question, I'm not sure why people are just giving you an answer to copy-paste.
Achieving the sum of numbers 1..10 is pretty simple. You will need to initialise an empty int var before your loop, and for each iteration from 0 up to and including 10 you will add your int var to the current iteration.
For example:
sum = 0;
for num in range 1 to 10:
sum = sum + num;
<?php
$start = 0; // set the variable that will hold our total
for($i=1;$i<11;$i++){ // set a loop, read here: http://php.net/manual/en/control-structures.for.php for more info
$start += $i; // add $i to our start value
}
echo $start; // display our final value
I would use a for loop.
$total = 0;
for($i = 1; $i <= 10; $i++){
$total += $i;
}
Using the for loop:
<?php
$sum = 0;
for($i = 1; $i <= 10; $i++){
$sum += $i;
}
Using the foreach loop:
<?php
$sum = 0;
foreach(range(1,10) as $num){
$sum += $num;
}
echo $sum; // prints 55
And disregarding your assignment, here is an easier way:
echo array_sum(range(1,10));