How to determine the first and last iteration in a foreach loop

Question

The question is simple  I have a foreach loop in my code   foreach  array as  element          code     In this loop  I want to react differently when we are in first or last iteration   How to do this

User · Accepted Answer

You could use a counter    i   0   len   count  array   foreach   array as  item        if   i    0               first       else if   i     len - 1               last                       i

User · Answer

For SQL query generating scripts  or anything that does a different action for the first or last elements  it is much faster  almost twice as fast  to avoid using unneccessary variable checks   The current accepted solution uses a loop and a check within the loop that will be made every single iteration  the correct  fast  way to do this is the following     numItems   count  arr    i 0   firstitem  arr 0    i    while  i lt  numItems-1        some item  arr  i        i       last item  arr  i    i      A little homemade benchmark showed the following   test1  100000 runs of model morg  time  1869 3430423737 milliseconds  test2  100000 runs of model if last  time  3235 6359958649 milliseconds  And it s thus quite clear that the check costs a lot  and of course it gets even worse the more variable checks you add

User · Answer

With Keys and Values this works as well   foreach   array as  key   gt   value        if   value     end  array             echo  LAST ELEMENT

User · Answer

1  Why not use a simple for statement  Assuming you re using a real array and not an Iterator you could easily check whether the counter variable is 0 or one less than the whole number of elements  In my opinion this is the most clean and understandable solution      array   array           count   count   array     for    i   0   i  lt   count   i             current    array   i         if    i    0                     process first element             if    i     count - 1                     process last element             2  You should consider using Nested Sets to store your tree structure  Additionally you can improve the whole thing by using recursive functions

User · Answer

The most efficient answer from  morg  unlike foreach  only works for proper arrays  not hash map objects  This answer avoids the overhead of a conditional statement for every iteration of the loop  as in most of these answers  including the accepted answer  by specifically handling the first and last element  and looping over the middle elements   The array keys function can be used to make the efficient answer work like foreach    keys   array keys  arr    numItems   count  keys    i 0    firstItem  arr  keys 0       Special handling of the first item goes here   i    while  i lt  numItems-1        item  arr  keys  i          Handling of regular items      i        lastItem  arr  keys  i       Special handling of the last item goes here   i      I haven t done benchmarking on this  but no logic has been added to the loop  which is were the biggest hit to performance happens  so I d suspect that the benchmarks provided with the efficient answer are pretty close   If you wanted to functionalize this kind of thing  I ve taken a swing at such an iterateList function here  Although  you might want to benchmark the gist code if you re super concerned about efficiency  I m not sure how much overhead all the function invocation introduces

User · Answer

If you prefer a solution that does not require the initialization of the counter outside the loop  I propose comparing the current iteration key against the function that tells you the last   first key of the array   This becomes somewhat more efficient  and more readable  with the upcoming PHP 7 3   Solution for PHP 7 3 and up   foreach  array as  key   gt   element        if   key     array key first  array           echo  FIRST ELEMENT         if   key     array key last  array           echo  LAST ELEMENT        Solution for all PHP versions   foreach  array as  key   gt   element        reset  array       if   key     key  array           echo  FIRST ELEMENT         end  array       if   key     key  array           echo  LAST ELEMENT

User · Answer

To find the last item  I find this piece of code works every time   foreach   items as  item         if   next   items               echo  Last Item

User · Answer

Best answer      arr   array 1  2  3  4  5  6  7  8  9  10    foreach   arr as  a        This is the line that does the checking if   each  arr   echo  End  n    echo  a   n

User · Answer

foreach   arquivos as  key   gt   item       reset  arquivos         FIRST AHEAD    if   key     key  arquivos      key     end array keys  arquivos            pdf- gt cat null  null   key          LAST    if   key     end array keys  arquivos              pdf- gt cat null  null   key             - gt execute

User · Answer

Using a Boolean variable is still the most reliable  even if you want to check the first appearance of a  value  I found it more useful in my situation and in many situations   such like this    is first   true   foreach   array as  value         switch    value             case  match               echo  appeared                if    is first                     echo  first appearance                    is first   false                             break                       if   next   array               echo  last value             Then how about  next   array   to find the last  value which will return true if there s no next   value to iterate   And I prefer to use a for loop instead of foreach if I were going to use a counter  like this    len   count   array    for    i   0   i  lt   len   i            value    array  i       if   i     0               first       elseif    i      len - 1                last                       i

User · Answer

An attempt to find the first would be    first   true   foreach    obj as  value       if    first              do something      first   false    in order not to get into the if statement for the next loops       else            do something else for all loops except the first

User · Answer

You can use the counter and array length         array   array 1 2 3 4         i   0       len   count  array       foreach   array as  item            if   i     0                   first           else if   i      len - 1                   last                                   i

User · Answer

Simply this works      Set the array pointer to the last key end  array      Store the last key  lastkey   key  array     foreach  array as  key   gt   element            do array stuff     if   lastkey     key  array           echo  THE LAST ELEMENT     array  lastkey       Thank you  billynoah for your sorting out the end issue

User · Answer

You can use an anonymous function  too    indexOfLastElement   count  array  - 1  array walk  array  function  element   index  use   indexOfLastElement           do something     if  0      index               first element   s treatment           if   indexOfLastElement      index               last not least             Three more things should be mentioned    If your array isn   t indexed strictly  numerically  you must pipe your array through array values first  If you need to modify the  element you have to pass it by reference   amp  element   Any variables from outside the anonymous function you need inside  you   ll have to list them next to  indexOfLastElement inside the use construct  again by reference if needed

User · Answer

A more simplified version of the above and presuming you re not using custom indexes      len   count  array   foreach   array as  index   gt   item        if   index    0               first       else if   index     len - 1               last           Version 2 - Because I have come to loathe using the else unless necessary    len   count  array   foreach   array as  index   gt   item        if   index    0               first            do something         continue             if   index     len - 1               last            do something         continue

User · Answer

Not sure if it still necessary  But the following solution should work with iterators and does not require count    lt  php  foreach first last array    function   key   value   step   first   last        echo intval  first        intval  last         step        value  PHP EOL       foreach first last array  aa    function   key   value   step   first   last        echo intval  first        intval  last         step        value  PHP EOL      echo PHP EOL   foreach first last array  aa    bb    cc    function   key   value   step   first   last        echo intval  first        intval  last         step        value  PHP EOL      echo PHP EOL   function foreach first last  array   cb         next   false       current   false      reset  array       for   step   0  true     step             current    next           next   each  array            last     next     false     next     null           if   step  gt  0                 first    step    1              list   key   value     current              if  call user func  cb   key   value   step   first   last      false                    break                                  if   last                break

User · Answer

You could remove the first and last elements off the array and process them separately     Like this    lt  php  array   something     first   array shift  array    last   array pop  array       do something with  first foreach   array as  item        do something with  item      do something with  last   gt    Removing all the formatting to CSS instead of inline tags would improve your code and speed up load time   You could also avoid mixing HTML with php logic whenever possible    Your page could be made a lot more readable and maintainable by separating things like this    lt  php function create menu  params        retrieve menu items      get collection     collection   get  xxcollection       foreach  collection as  c  show collection  c      function show subcat  val        gt       lt div class  sub node  style  display none  gt         lt img src     images dtree join gif  align  absmiddle  style  padding-left 2px     gt         lt a id     val  xsubcatid      href  javascript void 0   onclick  getProduct this   event   class  sub node links    gt           lt  php echo  val  xsubcatname      gt         lt  a gt       lt  div gt     lt  php    function show cat  item        gt       lt div class  node   gt         lt img src     images dtree plus gif  align  absmiddle  class  node item  id  plus    gt         lt img src     images dtree folder gif  align  absmiddle  id  folder  gt         lt  php echo  item  xcatname      gt         lt  php           subcat   get where  xxsubcategory    array  xcatid   gt  item  xcatid               foreach  subcat as  val  show subcat  val           gt       lt  div gt     lt  php    function show collection  c        gt       lt div class  parent  style  direction rtl  gt         lt img src     images dtree minus gif  align  absmiddle  class  parent item  id  minus    gt         lt img src     images dtree base gif  align  absmiddle  id  base  gt         lt  php echo  c  xcollectionname      gt         lt  php           get categories           cat   get where  xxcategory    array  xcollectionid   gt  c  xcollectionid              foreach  cat as  item  show cat  item           gt       lt  div gt     lt  php     gt

User · Answer

I came across this thread when I have the same problem  I only need to get the first element then I re-analyze my code until this came up to my mind    firstElement   true   foreach   reportData- gt result   as  row            if  firstElement    echo  first element    firstElement false              Other lines of codes here     The above codes are great and complete but if you only need just the first element then you may try this code

User · Answer

Try this   function children   amp  parents   parent   selected      if   parents  parent         list     lt ul gt         counter   count  parents  parent         class   array  first        foreach   parents  parent  as  child         if   child  id       selected    class      active         if   -- counter   class      last          list      lt li class      implode       class       gt  lt div gt  lt a href    id      child  id        alt       child  name        gt      child  name       lt  a gt  lt  div gt  lt  li gt           class   array           list    children  parents   child  id     selected              list      lt  ul gt        return  list         output    children   parents  0   p industry id

User · Answer

Using reset  array  and end  array    lt  php       arrays    1 2 3 4 5         first    reset  arrays        last     end  arrays            foreach   arrays as  array                  if    first     array                         echo   lt li gt   array  first lt  li gt                      else if    last     array                         echo   lt li gt   array  last lt  li gt                      else                       echo   lt li gt   array  lt  li gt                                       Demo repl it

[php] How to determine the first and last iteration in a foreach loop?

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