PHP: Adding prefix strings to array values

Question

What is the best way to add a specific value or values to an array? Kinda hard to explain, but this should help:

<?php
$myarray = array("test", "test2", "test3");
$myarray = array_addstuff($myarray, " ");
var_dump($myarray);
?>

Which outputs:

array(3) {
  [0]=>
  string(5) " test"
  [1]=>
  string(6) " test2"
  [2]=>
  string(6) " test3"
}

You could do so like this:

function array_addstuff($a, $i) {
    foreach ($a as &$e)
        $e = $i . $e;
    return $a;
}

But I'm wondering if there's a faster way, or if this function is built-in.

take a look at my answer, there is no a faster way, there is indeed a built in function, but for this implementation is proved to be slower — Daniel Andres Acevedo, Dec 13 '16 at 15:19

score 49 · Accepted Answer · edited Aug 04 '17 at 22:21

49

In the case that you're using a PHP version >= 5.3:

$array = array('a', 'b', 'c');
array_walk($array, function(&$value, $key) { $value .= 'd'; } );

edited Aug 04 '17 at 22:21

Talk Nerdy To Me

626
5
21

answered Dec 26 '10 at 23:29

Andre

3,150
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23

whats the & before the $value for? – GDY Jun 07 '19 at 07:02
1

@GDY: it means you're passing this parameter by reference and not by value (default behaviour) https://www.php.net/manual/en/language.references.pass.php – leochab Jan 13 '20 at 15:38
Technically, you're adding a suffix, not a prefix. Is there a more succinct way to do a prefix in the anonymous function besides `$value = ' ' . $value;`? – thelr May 11 '21 at 13:44
Like this one! Thank you. – Mr. Jo May 27 '21 at 14:10

score 31 · Answer 2 · answered Dec 27 '10 at 14:24

31

Use array_map()

$array = array('a', 'b', 'c');
$array = array_map(function($value) { return ' '.$value; }, $array);

answered Dec 27 '10 at 14:24

shfx

1,261
1
11
16

Wouldn't this have the overhead of creating a whole new array? – skeggse Jan 30 '14 at 01:40

score 14 · Answer 3 · edited Dec 13 '16 at 15:21

14

Below code will add "prefix_" as a prefix to each element value:

$myarray = array("test", "test2", "test3");    
$prefixed_array = preg_filter('/^/', 'prefix_', $myarray);

Output will be:

Array ( [0] => prefix_test [1] => prefix_test2 [2] => prefix_test3 )

edited Dec 13 '16 at 15:21

AD7six

63,116
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123

answered Mar 10 '16 at 13:39

manish

181
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4

2

Please add some explanation. As you have used variable names and literals which have no correspondence with the question, that is the least you could do. – trincot Mar 12 '16 at 22:55
1

What I have to add prefix at start and end of value? – Muhammad Hassaan Jan 24 '19 at 14:20

score 3 · Answer 4 · answered Dec 26 '10 at 23:28

3

Use array_walk. In PHP 5.3 you can use an anonymous to define that callback. Because you want to modify the actual array, you have to specify the first parameter of the callback as pass-by-reference.

answered Dec 26 '10 at 23:28

Oswald

31,254
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PHP: Adding prefix strings to array values

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