Split a string on every third instance of character - php

Question

How can I explode a string on every third semicolon (;)?
example data:
$string = 'piece1;piece2;piece3;piece4;piece5;piece6;piece7;piece8;';
Desired output:
$output[0] = 'piece1;piece2:piece3;'
$output[1] = 'piece4;piece5;piece6;'
$output[2] = 'piece7;piece8;'

Answer 1

I am sure you can do something slick with regular expressions, but why not just explode the each semicolor and then add them three at a time.
$tmp = explode(";", $string);
$i=0;
$j=0;
foreach($tmp as $piece) {
if(! ($i++ %3)) $j++; //increment every 3
$result[$j] .= $piece;
}

Answer 2

Easiest solution I can think of is:
$chunks = array_chunk(explode(';', $input), 3);
$output = array_map(create_function('$a', 'return implode(";",$a);'), $chunks);

Answer 3

Essentially the same solution as the other ones that explode and join again...
$tmp = explode(";", $string);
while ($tmp) {
$output[] = implode(';', array_splice($tmp, 0, 3));
};

Answer 4

$string = "piece1;piece2;piece3;piece4;piece5;piece6;piece7;piece8;piece9;";
preg_match_all('/([A-Za-z0-9\.]*;[A-Za-z0-9\.]*;[A-Za-z0-9\.]*;)/',$string,$matches);
print_r($matches);
Array
(
[0] => Array
(
[0] => piece1;piece2;piece3;
[1] => piece4;piece5;piece6;
[2] => piece7;piece8;piece9;
)
[1] => Array
(
[0] => piece1;piece2;piece3;
[1] => piece4;piece5;piece6;
[2] => piece7;piece8;piece9;
)
)

Answer 5

Maybe approach it from a different angle. Explode() it all, then combine it back in triples. Like so...
$str = "1;2;3;4;5;6;7;8;9";
$boobies = explode(";", $array);
while (!empty($boobies))
{
$foo = array();
$foo[] = array_shift($boobies);
$foo[] = array_shift($boobies);
$foo[] = array_shift($boobies);
$bar[] = implode(";", $foo) . ";";
}
print_r($bar);
Array
(
[0] => 1;2;3;
[1] => 4;5;6;
[2] => 7;8;9;
)

Answer 6

Here's a regex approach, which I can't say is all too good looking.
$str='';
for ($i=1; $i<20; $i++) {
$str .= "$i;";
}
$split = preg_split('/((?:[^;]*;){3})/', $str, -1,
PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
Output:
Array
(
[0] => 1;2;3;
[1] => 4;5;6;
[2] => 7;8;9;
[3] => 10;11;12;
[4] => 13;14;15;
[5] => 16;17;18;
[6] => 19;
)

Answer 7

Another regex approach.
<?php
$string = 'piece1;piece2;piece3;piece4;piece5;piece6;piece7;piece8';
preg_match_all('/([^;]+;?){1,3}/', $string, $m, PREG_SET_ORDER);
print_r($m);
Results:
Array
(
[0] => Array
(
[0] => piece1;piece2;piece3;
[1] => piece3;
)
[1] => Array
(
[0] => piece4;piece5;piece6;
[1] => piece6;
)
[2] => Array
(
[0] => piece7;piece8
[1] => piece8
)
)

Answer 8

Regex Split
$test = ";2;3;4;5;6;7;8;9;10;;12;;14;15;16;17;18;19;20";
// match all groups that:
// (?<=^|;) follow the beginning of the string or a ;
// [^;]* have zero or more non ; characters
// ;? maybe a semi-colon (so we catch a single group)
// [^;]*;? again (catch second item)
// [^;]* without the trailing ; (to not capture the final ;)
preg_match_all("/(?<=^|;)[^;]*;?[^;]*;?[^;]*/", $test, $matches);
var_dump($matches[0]);
array(7) {
[0]=>
string(4) ";2;3"
[1]=>
string(5) "4;5;6"
[2]=>
string(5) "7;8;9"
[3]=>
string(6) "10;;12"
[4]=>
string(6) ";14;15"
[5]=>
string(8) "16;17;18"
[6]=>
string(5) "19;20"
}

Answer 9

<?php
$str = 'piece1;piece2;piece3;piece4;piece5;piece6;piece7;piece8;';
$arr = array_map(function ($arr) {
return implode(";", $arr);
}, array_chunk(explode(";", $str), 3));
var_dump($arr);
outputs
array(3) {
[0]=>
string(20) "piece1;piece2;piece3"
[1]=>
string(20) "piece4;piece5;piece6"
[2]=>
string(14) "piece7;piece8;"
}

Answer 10

Similar to #Sebastian's earlier answer, I recommend preg_split() with a repeated pattern. The difference is that by using a non-capturing group and appending \K to restart the fullstring match, you can spare writting the PREG_SPLIT_DELIM_CAPTURE flag.
Code: (Demo)
$string = 'piece1;piece2;piece3;piece4;piece5;piece6;piece7;piece8;';
var_export(preg_split('/(?:[^;]*;){3}\K/', $string, 0, PREG_SPLIT_NO_EMPTY));
A similar technique for splitting after every 2 things can be found here. That snippet actually writes the \K before the last space character so that the trailing space is consumed while splitting.