I'm somewhat new to PHP, been reading a few books and I've never seen a loop where it gets you all the even numbers(for example from 1 to 10), so I decided to try it myself:
for($i=0;$i<10 && $i % 2===0;$i++)
echo $i;
Tried with only double == as well.
And this,
$i=0;
do echo $i; while($i++<10 && $i % 2 ==0);
Can't seem to figure out how to use 2 conditions in the same statement.
Would appreciate the help!
Thanks.
Try to use this code
for( $i=0; $i<=10; $i++ )
{
if( $i%2 == 0 ){
echo $i;
}
}
The loop is breaking entirely when the second condition fails the first time. On the first iteration: 0 is less than 10, and it is even, so the loop iterates. On the second iteration: 1 is less than 10, but is odd, so the loop breaks.
Your code is the equivalent of this:
for($i=0; $i<10; $i++) {
if ($i % 2 !==0 ) {
break;
}
echo $i;
}
0
You can eliminate the second condition of your for loop to prevent the breakage and rely exclusive on a third expression to increment $i by two each iteration.
for($i=0; $i<10; $i = $i + 2) {
echo $i;
}
02468
The second statement in a for-loop is/are the condition(s) which gets checked every loop. so if it fails your loop stops. what you need will look somewhat like this:
for ($i = 0; $i < 10; $i++)
if ($i % 2 == 0)
echo $i;
So the loop will run over every number but only print out the even ones.
You don't need to loop.
Range can create a range with third parameter step 2.
$arr = range(0,20,2);
Echo implode(" ", $arr);
https://3v4l.org/S3JWV
you can use also regular loop and get the evens by formula:
for($i=0; $i<10 ;$i++) {
$j = $i * 2;
// do somthing with $j witch loop over 10 first evens...
}
Related
what I am trying to achieve here is to be able to loop from 0 to 100 (100, 98, 96, 94 ...) but has to stop at 0. What is doing right now is it passes 0 and -2 -4 which crashes the server. What am I doing wrong?
for ($i = 100; $i <= 100; $i--){
echo $i--;
echo "<br>";
}
Maybe a little explanation would be useful.
The middle part of the for loop $i <= 100 is what makes it infinite. That expression is checked before each iteration of the loop, and the loop will continue as long as that expression evaluates to true.
Since you set $ito 100 in the first section of the loop, and you're doing nothing except making it smaller, it will always be <= 100, forever.
The loop will work fine just the way you have it written if you change the continuation condition.
for ($i = 100; $i >= 0; $i--){
echo $i--;
echo "<br>";
}
That way it will continue until $i is reduced to less than zero, then $i >= 0 will be false, and the loop will end.
The third argument in for loop is what will be executed at the end of the loop. So:
for ($i = 100; $i >= 0; $i -= 2){
echo "$i<br>";
}
Will do the trick
As you can read here https://secure.php.net/manual/en/control-structures.for.php
At the end of each iteration, expr3 is evaluated (executed).
Alternatively:
<?php
foreach(range(100, 0, -2) as $n) {
echo $n;
}
for ($i = 100; $i >= 0; $i-=1){
echo $i--;
echo "<br>";
}
I figured it out somehow. Has been studying JavaScript for a year; Loop is still confusing to me
I am taking a demo test at codility.com.
I tried the following PHP test code:
function solution($A) {
$min = 0;
$size = count($A)-1;
for($i=0;$i<5;$i++){
if($i=0)
$min=$A[0];
}
return $min;
}
The script takes around 3.03s to execute where they have set the maximum execution time to 2.00s.
And if i comment the FOR LOOP it works properly.
Any idea ?
You are overwritting your $i variable here:
if($i=0)
it should be
if($i==0)
because you have wirte if($i=0) it is assignment operator not comparision operator. make it correct if($i==0)
function solution($A) {
$min = 0;
$size = count($A)-1;
for($i=0;$i<5;$i++){
if($i==0)
$min=$A[0];
}
return $min;
}
Your for loop looks like this:
for($i = 0; $i < 5; $i++)
This means: initialize $i to 0, and until $i is 5 or more, execute the loop and increment $i.
But, you wrote this:
if($i = 0)
To compare $i and 0, you should've used ==, not =. This sets $i to 0. The if is not executed, as 0 is equal to false. Then $i is incremented to 1. 1 is less than 5, so the loop is executed forever.
Use if($i == 0) to fix it.
There is a mistake that everyone has pointed out which is if($i=0) should be if($i==0).
But I have one concern. Why there is a for loop when it is simply returning $min which is $A[0] ?
Could someone help suggest in below php explode function, we are displaying script after 5th listing. How is it possible to display script exactly after 5th listing and 10th listing on a page which has more than 10 listings
We tried using
if ($i == 5 & $i== 10)
but it does not work
Below is original code - which displays script after 5th listing
<?php
$listings = explode("<hr/>", $list);
$numberOfListings = count($listings);
for($i = 0; $i < $numberOfListings; ++$i)
{
if ($i == 5)
{ ?>
<script> </script>
<?php }
echo $listings[$i] . "<hr/>";
}
?>
Edit
How is it like - if have to display a separate script on $i==9, could you advise.
Because $i starts at 0 (0 to 9 is 10, whilst 0 to 10 is 11). Try if ($i == 4 || $i== 9), with an or operator.
Also I would not use the && (the and operator), because it is unlikely $i will ever equal both 4 and 9. I'd suggest you read into Truth Tables (and maybe Propositional Calculus) because from seeing what you had tried originally, it would be helpful to understand how a truth table works.
(source: wlc.edu)
You can use the contine, continue is used within looping structures to skip the rest of the current loop iteration and continue execution at the condition evaluation and then the beginning of the next iteration.
$arr = range(0,9);
foreach($arr as $number) {
if($number < 5) {
continue;
}
print $number;
}
Ref: http://php.net/manual/en/control-structures.continue.php
Try using modulus operator
$listings = explode("<hr/>", $list);
$numberOfListings = count($listings);
for($i = 1; $i < $numberOfListings; ++$i)
{
if ($i%5 == 0)
{
echo "in";
?>
<script> </script>
<?php
}
echo $listings[$i-1] . "<hr/>";
}
Here we are looping from 1 and there for $i <= $numberOfListings
and while listing we will use $listings[$i-1]
DEMO CODE AT http://codepad.viper-7.com/lrTOgP
I have a string called $columns which dynamically gets a value from 1 to 7. I want to create a loop of <td></td> for however many times the value of $columns is. Any idea how I can do this?
for ($k = 0 ; $k < $columns; $k++){ echo '<td></td>'; }
Here's a more readable way to achieve this:
foreach(range(1,$columns) as $index) {
//do your magic here
}
If you just need to use number of repeat count:
for ($i = 0; $i < 5; $i++){
// code to repeat here
}
just repeat $n times? ... if dont mind that $n goes backwards...
the advantage is that you can see/config "times" at the beginning
$n = 5;
while (--$n >= 0)
{
// do something, remember that $n goes backwards;
}
I like this way:
while( $i++ < $columns ) echo $i;
Just bear in mind if $columns is 5, this will run 5 times (not 4).
Edit: There seems to be some confusion around the initial state of $i here. You are welcome to initialise $i=0 beforehand if you wish. This is not required however as PHP is a very helpful engine and will do it for you automatically (tho, it will throw a notice if you happen to have those enabled).
There is a str_repeat() function in PHP, which repeats a string a number of times. The solution for your problem would be:
str_repeat( '<td></td>', $columns );
If $columns is a string you can cast to int and use a simple for loop
for ($i=1; $i<(int)$columns; $i++) {
echo '<td></td>';
}
A for loop will work:
for ($i = 0; $i < $columns; $i++) {
...
}
You can run it through a for loop easily to achieve this
$myData = array('val1', 'val2', ...);
for( $i = 0; $i < intval($columns); $i++)
{
echo "<td>" . $myData[$i] . "</td>";
}
Why use logic at all, don't waste those CPU cycles!
<td colspan="<?php echo $columns; ?>"></td>
How to do something every 5 (for example) cycles inside foreach?
I'm add $i++ How to check it by step?
Use modulo to determine offset.
$i = 0;
foreach ($array as $a) {
$i++;
if ($i % 5 == 0) {
// your code for every 5th item
}
// your inside loop code
}
Unless you're doing something separately in each iteration, don't.
Use a for loop and increment the counter by 5 each time:
$collectionLength = count($collection);
for($i = 0; $i < $collectionLength; i+=5)
{
// Do something
}
Otherwise, you can use the modulo operator to determine if you're on one of the fifth iterations:
if(($i + 1) % 5 == 0) // assuming i starts at 0
{
// Do something special this time
}
for($i = 0; $i < $items; $i++){
//for every 5th item, assuming i starts at 0 (skip)
if($i % 5 == 0 && $i != 0){
//execute your code
}
}