Get next element in foreach loop

Question

I have a foreach loop and I want to see if there is a next element in the loop so I can compare the current element with the next  How can I do this  I ve read about the current and next functions but I can t figure out how to use them   Thanks in advance

User · Answer

If the indexes are continuous   foreach   arr as  key   gt   val       if  isset  arr  key 1            echo  arr  key 1      next element      else           end of array reached

User · Answer

You could get the keys values and index   lt  php  a   array       key1   gt  value1         key2   gt  value2         key3   gt  value3         key4   gt  value4         key5   gt  value5       keys   array keys  a   foreach array keys  keys  as  index                current key   current  keys      or  current key    keys  index        current value    a  current key      or  current value    a  keys  index          next key   next  keys         next value    a  next key     null     for php version  gt   7 0      echo     index   current      current key    gt    current value    next      next key    gt    next value   n       result   0  current    key1   gt  value1   next    key2   gt  value2   1  current    key2   gt  value2   next    key3   gt  value3   2  current    key3   gt  value3   next    key4   gt  value4   3  current    key4   gt  value4   next    key5   gt  value5   4  current    key5   gt  value5   next       gt

User · Answer

You could get the keys of the array before the foreach  then use a counter to check the next element  something like      arr is the array you wish to cycle through  keys   array keys  arr    num keys   count  keys    i   1  foreach   arr as  a        if   i  lt   num keys  amp  amp   arr  keys  i       a                   we have a match            i        This will work for both simple arrays  such as array 1 2 3   and keyed arrays such as array  first   gt 1   second   gt 2   thrid   gt 3

User · Answer

A unique approach would be to reverse the array and then loop   This will work for non-numerically indexed arrays as well    items   array       one      gt   two        two      gt   two        three    gt   three      backwards   array reverse  items    last item   NULL   foreach   backwards as  current item        if   last item      current item               they match            last item    current item      If you are still interested in using the current and next functions  you could do this    items   array  two    two    three     length   count  items   for  i   0   i  lt   length - 1     i        if  current  items      next  items                they match            2 is probably the best solution   Note   i  lt   length - 1  will stop the loop after comparing the last two items in the array   I put this in the loop to be explicit with the example   You should probably just calculate  length   count  items  - 1

User · Answer

if its numerically indexed   foreach   foo as  key  gt  var        if  var   foo  key 1            echo  current and next var are the same

User · Answer

The general solution could be a caching iterator  A properly implemented caching iterator works with any Iterator  and saves memory  PHP SPL has a CachingIterator  but it is very odd  and has very limited functionality  However  you can write your own lookahead iterator like this    lt  php  class NeighborIterator implements Iterator        protected  oInnerIterator       protected  hasPrevious   false      protected  previous   null      protected  previousKey   null       protected  hasCurrent   false      protected  current   null      protected  currentKey   null       protected  hasNext   false      protected  next   null      protected  nextKey   null       public function   construct Iterator  oInnerIterator                 this- gt oInnerIterator    oInnerIterator             public function current                 return  this- gt current             public function key                 return  this- gt currentKey             public function next                 if   this- gt hasCurrent                 this- gt hasPrevious   true               this- gt previous    this- gt current               this- gt previousKey    this- gt currentKey               this- gt hasCurrent    this- gt hasNext               this- gt current    this- gt next               this- gt currentKey    this- gt nextKey              if   this- gt hasNext                     this- gt oInnerIterator- gt next                     this- gt hasNext    this- gt oInnerIterator- gt valid                    if   this- gt hasNext                         this- gt next    this- gt oInnerIterator- gt current                         this- gt nextKey    this- gt oInnerIterator- gt key                      else                        this- gt next   null                       this- gt nextKey   null                                                       public function rewind                  this- gt hasPrevious   false           this- gt previous   null           this- gt previousKey   null           this- gt oInnerIterator- gt rewind             this- gt hasCurrent    this- gt oInnerIterator- gt valid            if   this- gt hasCurrent                 this- gt current    this- gt oInnerIterator- gt current                 this- gt currentKey    this- gt oInnerIterator- gt key                 this- gt oInnerIterator- gt next                 this- gt hasNext    this- gt oInnerIterator- gt valid                if   this- gt hasNext                     this- gt next    this- gt oInnerIterator- gt current                     this- gt nextKey    this- gt oInnerIterator- gt key                  else                    this- gt next   null                   this- gt nextKey   null                          else                this- gt current   null               this- gt currentKey   null               this- gt hasNext   false               this- gt next   null               this- gt nextKey   null                       public function valid                 return  this- gt hasCurrent             public function hasNext                 return  this- gt hasNext             public function getNext                 return  this- gt next             public function getNextKey                 return  this- gt nextKey             public function hasPrevious                 return  this- gt hasPrevious             public function getPrevious                 return  this- gt previous             public function getPreviousKey                 return  this- gt previousKey             header  Content-type  text plain  charset utf-8     arr          a    gt   alma        b    gt   banan        c    gt   cseresznye        d    gt   dio        e    gt   eper       oNeighborIterator   new NeighborIterator new ArrayIterator  arr    foreach   oNeighborIterator as  key   gt   value            you can get previous and next values       if    oNeighborIterator- gt hasPrevious              echo   FIRST  n             echo  oNeighborIterator- gt getPreviousKey         gt       oNeighborIterator- gt getPrevious       ----- gt                echo         key       gt       value              ----- gt         echo  oNeighborIterator- gt getNextKey         gt       oNeighborIterator- gt getNext       n       if    oNeighborIterator- gt hasNext              echo   LAST  n

User · Answer

You could probably use while loop instead of foreach   while   current   current  array           next   next  array       if  false      next  amp  amp   next     current                  do something with  current

User · Answer

As php net foreach points out      Unless the array is referenced  foreach operates on a copy of the specified array and not the array itself  foreach has some side effects on the array pointer  Don t rely on the array pointer during or after the foreach without resetting it    In other words - it s not a very good idea to do what you re asking to do  Perhaps it would be a good idea to talk with someone about why you re trying to do this  see if there s a better solution  Feel free to ask us in   PHP on irc freenode net if you don t have any other resources available

User · Answer

A foreach loop in php will iterate over a copy of the original array  making next   and prev   functions useless  If you have an associative array and need to fetch the next item  you could iterate over the array keys instead   foreach  array keys  items  as  index   gt   key           first  get current item      item    items  key          now get next item in array      next    items array keys  items   index   1        Since the resulting array of keys has a continuous index itself  you can use that instead to access the original array   Be aware that  next will be null for the last iteration  since there is no next item after the last  Accessing non existent array keys will throw a php notice  To avoid that  either    Check for the last iteration before assigning values to  next Check if the key with index   1 exists with array key exists     Using method 2 the complete foreach could look like this   foreach  array keys  items  as  index   gt   key           first  get current item      item    items  key          now get next item in array      next   null      if  array key exists  index   1  array keys  items               next    items array keys  items   index   1

[php] Get next element in foreach loop

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