Add prefix string to each value of a flat array

Question

What is the best way to add a specific value or values to an array?

<?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.

Talk Nerdy To Me · Accepted Answer · 2017-08-04 22:21:08Z

52

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 4, 2017 at 22:21

Talk Nerdy To Me

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answered Dec 26, 2010 at 23:29

Andre

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3 Comments

GDY Over a year ago

whats the & before the $value for?

leochab Over a year ago

@GDY: it means you're passing this parameter by reference and not by value (default behaviour) php.net/manual/en/language.references.pass.php

thelr Over a year ago

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;?

shfx · Accepted Answer · 2010-12-27 14:24:32Z

35

Use array_map()

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

answered Dec 27, 2010 at 14:24

shfx

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1 Comment

skeggse Over a year ago

Wouldn't this have the overhead of creating a whole new array?

AD7six · Accepted Answer · 2016-12-13 15:21:41Z

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, 2016 at 15:21

AD7six

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answered Mar 10, 2016 at 13:39

manish

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2 Comments

trincot Over a year ago

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.

Hassaan Over a year ago

What I have to add prefix at start and end of value?

Oswald · Accepted Answer · 2010-12-26 23:28:33Z

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, 2010 at 23:28

Oswald

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Comments

mickmackusa · Accepted Answer · 2024-09-18 02:36:42Z

2

PHP already has a native function to replace your array_addstuff() function and it doesn't need regex --substr_replace().

Starting from the 0 offset, replace 0 characters with a space.

Code: (Demo)

$myarray = ["test", "test2", "test3"];

var_export(
    substr_replace($myarray, ' ', 0, 0)
);

Output:

array (
  0 => ' test',
  1 => ' test2',
  2 => ' test3',
)

edited Sep 18, 2024 at 2:36

answered Mar 23, 2024 at 12:22

mickmackusa♦

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