Fastest way to implode an associative array with keys

Question

I'm looking for a fast way to turn an associative array in to a string. Typical structure would be like a URL query string but with customizable separators so I can use '&' for xhtml links or '&' otherwise.

My first inclination is to use foreach but since my method could be called many times in one request I fear it might be too slow.

<?php
$Amp = $IsXhtml ? '&amp;' : '&';
$Parameters = array('Action' => 'ShowList', 'Page' => '2');
$QueryString = '';
foreach ($Parameters as $Key => $Value)
        $QueryString .= $Amp . $Key . '=' . $Value;

Is there a faster way?

Don't forget if you are outputting HTML, the correct syntax is & not &, iow this is wrong <a href="?name=joe&age=22">JOE</a> yes it works but it's invalid HTML. — TravisO
– TravisO, Commented Jan 6, 2009 at 18:21

Sergiu Dumitriu · Accepted Answer · 2013-01-05 07:24:41Z

189

You can use http_build_query() to do that.

Generates a URL-encoded query string from the associative (or indexed) array provided.

edited Jan 5, 2013 at 7:24

Sergiu Dumitriu

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answered Jan 2, 2009 at 21:09

Greg

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6 Comments

Mark Davidson Over a year ago

Was trying to find this method in the PHP API myself this is definitely the way to go. If not the alternative is to use a modified implode method such as uk2.php.net/manual/en/function.implode.php#84684 but http_build_query() will properly be faster.

e-motiv Over a year ago

I wonder if this is really the fastest way for the general question. There is some encoding going on in this function. So, if it's not for a URL, is this really faster than array_walk and what if you don't want it encoded?

Sisyphus Over a year ago

the problem is http_build_query escape special char

ErnestV Over a year ago

I've compared serialize(), json_encode() and http_build_query(). http_build_query() won by a slight margin over serialize(), and json_encode being the slowest by far.

awavi Over a year ago

It also encodes special characters, so this is not a good option

|

scunliffe · Accepted Answer · 2014-10-12 03:12:17Z

46

If you're not concerned about the exact formatting however you do want something simple but without the line breaks of print_r you can also use json_encode($value) for a quick and simple formatted output. (note it works well on other data types too)

$str = json_encode($arr);
//output...
[{"id":"123","name":"Ice"},{"id":"234","name":"Cake"},{"id":"345","name":"Pie"}]

answered Oct 12, 2014 at 3:12

scunliffe

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Comments

Adam · Accepted Answer · 2009-02-03 14:06:21Z

36

As an aside, I was in search to find the best way to implode an associative array but using my own seperators etc...

So I did this using PHP's array_walk() function to let me join an associative array into a list of parameters that could then be applied to a HTML tag....

// Create Params Array
$p = Array("id"=>"blar","class"=>"myclass","onclick"=>"myJavascriptFunc()");

// Join Params
array_walk($p, create_function('&$i,$k','$i=" $k=\"$i\"";'));
$p_string = implode($p,"");

// Now use $p_string for your html tag

Obviously, you could stick that in your own function somehow but it gives you an idea of how you can join an associative array using your own method. Hope that helps someone :)

answered Feb 3, 2009 at 14:06

Adam

3 Comments

Matt Fletcher Over a year ago

If the syntax of create_function is confusing anyone, see php.net/manual/en/function.create-function.php

Enyby Over a year ago

array_walk is slower from foreach and more complicated for read. See this: reddit.com/r/PHP/comments/1uuc34/…

Ernesto Allely Over a year ago

Found this version useful as the first solution as http_build_query() encodes URLs.

user4846194 · Accepted Answer · 2015-04-29 11:41:20Z

24

This is my solution for example for an div data-attributes:

<?

$attributes = array(
    'data-href'   => 'http://example.com',
    'data-width'  => '300',
    'data-height' => '250',
    'data-type'   => 'cover',
);

$dataAttributes = array_map(function($value, $key) {
    return $key.'="'.$value.'"';
}, array_values($attributes), array_keys($attributes));

$dataAttributes = implode(' ', $dataAttributes);

?>

<div class="image-box" <?= $dataAttributes; ?> >
    <img src="http://example.com/images/best-of.jpg" alt="">
</div>

answered Apr 29, 2015 at 11:41

user4846194

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Comments

Raptor · Accepted Answer · 2013-05-30 02:42:54Z

21

One way is using print_r(array, true) and it will return string representation of array

edited May 30, 2013 at 2:42

Raptor

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answered Jan 5, 2013 at 15:13

dino.keco

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2 Comments

zzapper Over a year ago

$request_str=print_r($_REQUEST,true); // flatten array for log file

Rikki Over a year ago

But that outputs in the print_r format, not as key=value joined with a supplied separator.

kostikovmu · Accepted Answer · 2019-06-19 15:29:03Z

10

My solution:

$url_string = http_build_query($your_arr);
$res = urldecode($url_string);

answered Jun 19, 2019 at 15:29

kostikovmu

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1 Comment

fekiri malek Over a year ago

i liked this approach as it looks simpler than other long codes. though this is not exactly what we are after.. we look for this format : "key: value\r\n...." so i used this fomula : to get that urldecode(str_replace("=", ": ", http_build_query($headers,"", "\r\n"))). look below for this as proposed solution.

Frantisek Hallo · Accepted Answer · 2017-11-08 20:36:29Z

3

What about this shorter, more transparent, yet more intuitive with array_walk

$attributes = array(
  'data-href'   => 'http://example.com',
  'data-width'  => '300',
  'data-height' => '250',
  'data-type'   => 'cover',
);

$args = "";
array_walk(
    $attributes, 
    function ($item, $key) use (&$args) {
        $args .= $key ." = '" . $item . "' ";  
    }
);
// output: 'data-href="http://example.com" data-width="300" data-height="250" data-type="cover"

edited Nov 8, 2017 at 20:36

answered Nov 3, 2017 at 16:21

Frantisek Hallo

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Comments

Softmixt · Accepted Answer · 2015-07-28 10:25:08Z

2

function array_to_attributes ( $array_attributes )
{

    $attributes_str = NULL;
    foreach ( $array_attributes as $attribute => $value )
    {

        $attributes_str .= " $attribute=\"$value\" ";

    }

    return $attributes_str;
}

$attributes = array(
    'data-href'   => 'http://example.com',
    'data-width'  => '300',
    'data-height' => '250',
    'data-type'   => 'cover',
);

echo array_to_attributes($attributes) ;

answered Jul 28, 2015 at 10:25

community wiki

Softmixt

Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

2

A one-liner for creating string of HTML attributes (with quotes) from a simple array:

$attrString = str_replace("+", " ", str_replace("&", "\" ", str_replace("=", "=\"", http_build_query($attrArray)))) . "\"";

Example:

$attrArray = array("id"    => "email", 
                   "name"  => "email",
                   "type"  => "email",
                   "class" => "active large");

echo str_replace("+", " ", str_replace("&", "\" ", str_replace("=", "=\"", http_build_query($attrArray)))) . "\"";

// Output:
// id="email" name="email" type="email" class="active large"

edited Jun 20, 2020 at 9:12

CommunityBot

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answered Apr 27, 2017 at 18:30

WackGet

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Comments

Unicco · Accepted Answer · 2022-03-03 11:29:01Z

1

Use array_walk for this.

$arr = [
    "key"  => "value",
    "key2" => "value2",
];

array_walk($arr, function(&$value, $key) {
    $value = "{$key}: {$value}";
});

implode("<br/>", $arr)

Result

key: value<br/>key2: value2<br/>

answered Mar 3, 2022 at 11:29

Unicco

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Comments

fekiri malek · Accepted Answer · 2023-02-15 23:29:02Z

0

I liked the approach of @kostikovmu as it looks simpler than other long codes. though this is not exactly what we are after.. We look for this header format : "...key: value\r\n...".

So i used extended the fomula to get that

urldecode(str_replace("=", ": ", http_build_query($headers,"", "\r\n")))

answered Feb 15, 2023 at 23:29

fekiri malek

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