如何跳过foreach循环中的元素

Question

I want to skip some records in a foreach loop.

For example, there are 68 records in the loop. How can I skip 20 records and start from record #21?

Answer 1

Five solutions come to mind:

Double addressing via array_keys

The problem with for loops is that the keys may be strings or not continues numbers therefore you must use "double addressing" (or "table lookup", call it whatever you want) and access the array via an array of it's keys.

// Initialize 25 items
$array = range( 1, 25, 1);

// You need to get array keys because it may be associative array
// Or it it will contain keys 0,1,2,5,6...
// If you have indexes staring from zero and continuous (eg. from db->fetch_all)
// you can just omit this
$keys = array_keys($array);
for( $i = 21; $i < 25; $i++){
    echo $array[ $keys[ $i]] . "\n";
    // echo $array[$i] . "\n"; // with continuous numeric keys
}

---

Skipping records with foreach

I don't believe that this is a good way to do this (except the case that you have LARGE arrays and slicing it or generating array of keys would use large amount of memory, which 68 is definitively not), but maybe it'll work: :)

$i = 0;
foreach( $array as $key => $item){
    if( $i++ < 21){
        continue;
    }
    echo $item . "\n";
}

---

Using array slice to get sub part or array

Just get piece of array and use it in normal foreach loop.

$sub = array_slice( $array, 21, null, true);
foreach( $sub as $key => $item){
    echo $item . "\n";
}

---

Using next()

If you could set up internal array pointer to 21 (let's say in previous foreach loop with break inside, $array[21] doesn't work, I've checked :P) you could do this (won't work if data in array === false ):

while( ($row = next( $array)) !== false){
  echo $row;
}

_{btw: I like hakre's answer most.}

---

Using ArrayIterator

Probably studying documentation is the best comment for this one.

// Initialize array iterator
$obj = new ArrayIterator( $array);
$obj->seek(21); // Set to right position
while( $obj->valid()){ // Whether we do have valid offset right now
    echo $obj->current() . "\n";
    $obj->next(); // Switch to next object
}

Answer 2

$i = 0;
foreach ($query)
{
  if ($i++ < 20) continue;

  /* php code to execute if record 21+ */
}

Answer 3

if want to skipped some index then make an array with skipped index and check by in_array function inside the foreach loop if match then it will be skip.

Example:

//you have an array like that
$data = array(
    '1' => 'Hello world',
    '2' => 'Hello world2',
    '3' => 'Hello world3',
    '4' => 'Hello world4',
    '5' => 'Hello world5',// you want to skip this
    '6' => 'Hello world6',// you want to skip this
    '7' => 'Hello world7',
    '8' => 'Hello world8',
    '9' => 'Hello world8',
    '10' => 'Hello world8',//you want to skip this
);

//Ok Now wi make an array which contain the index wich have to skipped

$skipped = array('5', '6', '10');

foreach($data as $key => $value){
    if(in_array($key, $skipped)){
        continue;
    }
    //do your stuf
}

Answer 4

You have not told what "records" actually is, so as I don't know, I assume there is a RecordIterator available (if not, it is likely that there is some other fitting iterator available):

$recordsIterator = new RecordIterator($records);
$limited = new LimitIterator($recordsIterator, 20);
foreach($limited as $record)
{
    ...
}

The answer here is to use foreach with a LimitIterator .

See as well: How to start a foreach loop at a specific index in PHP

Answer 5

I'm not sure why you would be using a foreach for this goal, and without your code it's hard to say whether this is the best approach. But, assuming there is a good reason to use it, here's the smallest version I can think of off the top of my head:

$count = 0;
foreach( $someArray as $index => $value ){
    if( $count++ < 20 ){
        continue;
    }

    // rest of foreach loop goes here
}

The continue causes the foreach to skip back to the beginning and move on to the next element in the array. It's extremely useful for disregarding parts of an array which you don't want to be processed in a foreach loop.

Answer 6

    array.forEach(function(element,index){
        if(index >= 21){
            //Do Something
        }
    });

Element would be the current value of index. Index increases with each turn through the loop. IE 0,1,2,3,4,5; array[index];

Answer 7

for($i = 20; $i <= 68; $i++){
//do stuff
}

This is better than a foreach loop because it only loops over the elements you want. Ask if you have any questions