I am aware we can skip the next iteration with continue in a for loop. Anyway to skip the next x loops (2 or more)?
You actually can't, you can do a dirty trick like
for ($i=0; $i<99; $i++){
if(someCondition) {
$i = $i + N; // This will sum N+1 because of the $i++ in the for iterator (that fire when the new loop starts)
continue;
}
}
If you're iterating with a for loop (as opposed to a foreach loop) you could do something like this:
for ($i=0; $i<$numLoops; $i++) {
if(condition()) {
$i+= $numLoopsToSkip;
continue;
}
}
Take for example, you can define the amount of times you want to loop as you want as $y
<?php
y = 5;
while (true) {
// do something
if (y > 0) {
y--;
continue;
}
// do something else
}
?>
Coming soon in PHP 'X' ;-)
continue += x;
Related
I'm somewhat new to PHP, been reading a few books and I've never seen a loop where it gets you all the even numbers(for example from 1 to 10), so I decided to try it myself:
for($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...
}
Newb question: I'm using a foreach loop to get items from an array.
I need to start looping at an offset number- (I'm using a $i variable to do this, no problem).
But when my foreach reaches the end of the array I want it to start going through the array again until it reaches the offset number.
I need to do this so I can have a user open any image in an artist's portfolio and have this image used as the first image presented in a grid of thumbnail icons , with all the other images subsequently populating the rest of the grid.
Any ideas?
Please bear in mind I'm new to PHP! :)
See below for an example of my current code...
$i=0;
$limit=50;// install this in the if conditional with the offset in it (below) to limit the number of thumbnails added to the page.
$offset=$any_arbitrary_link_dependant_integer;
foreach($portfolio_image_array as $k=>$image_obj){//$k = an integer counter, $image_obj = one of the many stored imageObject arrays.
$i++;
if ($i > $offset && $i < $limit) {// ignore all portfolio_array items below the offset number.
if ($img_obj->boolean_test_thing===true) {// OK as a way to test equivalency?
// do something
} else if ($img_obj->boolean_test_thing===false) { // Now add all the non-see_more small thumbnails:
// do something else
} else {
// error handler will go here.
}
} // end of offset conditional
}// end of add boolean_test_thing thumbnails foreach loop.
};// end of add thumbnails loop.
$i = 0;
$limit = 50;
$offset = $any_arbitrary_link_dependant_integer;
$count = count($portfolio_image_array);
foreach($portfolio_image_array as $k=>$image_obj){//$k = an integer counter, $image_obj = one of the many stored imageObject arrays.
$i++;
if ($i > $offset && $i < $limit && $i < ($count - $offset)) {// ignore all portfolio_array items below the offset number.
if ($img_obj->boolean_test_thing===true) {// OK as a way to test equivalency?
// do something
} else if ($img_obj->boolean_test_thing===false) { // Now add all the non-see_more small thumbnails:
// do something else
} else {
// error handler will go here.
}
} // end of offset conditional
}// end of add boolean_test_thing thumbnails foreach loop.
};
Only thing I added was a $count variable.
Edit: If your array starts at 0 I would suggest you put the $i++; at the end of your foreach loop.
A simple method is to use two separate numeric for loops, the first going from offset to end, and the second going from beginning to offset.
<?php
// Create an example array - ignore this line
$example = array(1,2,3,4,5,6);
$offset = 3;
// Standard loop stuff
$count = count($example);
for($i = $offset; $i < $count; $i++)
{
echo $example[$i]."<br />";
}
for($i = 0; $i < $offset; $i++)
{
echo $example[$i]."<br />";
}
?>
This is also almost certainly cheaper than doing multiple checks on every single element in the array, and it expresses exactly what you are trying to do to other programmers who look at this code - including yourself in 2 weeks time.
Edit: depending on the nature of the array, in order to use numeric keys you may first need to do $example = array_values($portfolio_image_array);.
Using Answer Question to force StackOverflow to let me post a decent length of text!
OK #Mark Walet et al, not sure how to post correctly on this forum yet but here goes. I got the issue sorted as follows:
$i=0;
$offset=$image_to_display_number;
$array_length = count($portfolio_image_array);
// FIRST HALF LOOP:
foreach($portfolio_image_array as $k=>$img_obj){// go through array from offset (chosen image) to end.
if ($i >= $offset && $i <= $array_length) {
echo write_thumbnails_fun($type_of_thumbnail, $image_path, $k, $i, $portfolio_image_array, $title, $image_original);
$t_total++;// update thumbnail total count.
}
$i++;
}// end of foreach loop 1.
$looped=true;// Just FYI.
$i=0;// Reset.
// SECOND HALF LOOP:
foreach($portfolio_image_array as $k=>$img_obj){// go through array from beginning to offset.
if ($i < $offset) {
echo write_thumbnails_fun($type_of_thumbnail, $image_path, $k, $i, $portfolio_image_array, $title, $image_original);
}
$i++;
}// end of foreach loop 2.
Thankyou so much for all the help!
:)
as #arkascha suggested use modulo operator
<?php
$example = array(1,2,3,4,5,6);
$count = count($example);
$offset = 3;
for($i = 0; $i < $count; $i++) {
$idx = ($offset + $i) % count
echo $example[$idx]."<br />";
}
?>
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
}
}
I have a while loop that contains an if statement. The while loop works fine but when I run the following if statement for each value passed through the while loop, and the if statement returns true, the script hangs up and I get the 30 second maximum execution time error.
I am not sure if it is creating an infinite loop or what. Can anyone spot the problem?
$size = count($_POST['itemname']);
// start a loop in order to update each record
$i = 0;
while ($i < $size) {
// define each variable
$itemname= $_POST['itemname'][$i];
$id = $_POST["id"][$i];
if(preg_match('/[A-Za-z]/',$itemname)) {
echo("has words");
} else {
//update code here
}
}
You never increment $i, that is what is hanging it up as it will always be < $size
while ($i < $size) { // changed this to >
// define each variable
$itemname= $_POST['itemname'][$i];
$id = $_POST["id"][$i];
$i++; // increment $i
You never increment $i. Try a for loop instead; they're a little more explicit.
You need to increment $i somewhere outside of the if statement.
you never change $i in the while loop
you have to increment $i for each loop or else if its true once it will always pass
add $i++ between the last 2
}
}
so it looks
}
$i++;
}
I'm working on custom pagination system and encountered following problem. When one of the elements is filtered out of the set, the size of the final array is smaller than needed. Therefore I'm looking for a solution to increase the number of iterations from within the loop to always get array consisting of 50 elements.
$limit = 50; //Number of elements I want to fetch
for($x=0; $x<$limit; $x++){
if ($elementIsNotFiltered) {
//add element to $someArray;
}
else {
//increase the number of iterations, so even if some elements are filtered out,
//the size of $someArray will always be 50
}
}
Thanks for any help.
Do it in a while() loop instead, and break when you finally hit your $limit
Use a while loop.
while(count($somearray) < 50 && /*elements remain*/) ...
else {
++$limit;
}
Tried that?
You may also do the same thing the other way round:
else {
--$x;
}
Or be a little bit more effective:
$x = 0;
while ($x != 50) {
if ($notFiltered) {
++$x;
}
}
If you want to save the counter variable, too, you may use:
while (!isset($array[49])) {
}
The !isset($array[49]) here is only a synonym of count($array) < 50.
It sounds to me like you're looking for a while loop - not a for loop:
while ($items < 50 && [more items to filter]) {
if ([add to array]) {
$items++;
}
}
If you really want to do it in your for loop you can always modify $x but this makes your code unreadable and hard to maintain - I would recommend not doing this...