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?

Dunlap

Don't forget if you are outputting HTML, the correct syntax is &amp; not &, iow this is wrong <a href="?name=joe&age=22">JOE</a> yes it works but it's invalid HTML. – Toodleoo

Answer 1

You can use http_build_query() to do that.

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

Shive

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. – Wheelwright

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? – Harmonious

the problem is http_build_query escape special char – Delenadeleon

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. – Materialist

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

to commenters, what if you don't need any special chars? Then this solution is perfect – Reasoned

Answer 2

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"}]

Myrmecology

Answer 3

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 :)

Semester

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

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

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

Answer 4

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>

Periclean

Answer 5

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

Backman

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

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

Answer 6

My solution:

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

Substantial

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. – Toweling

Answer 7

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"

Asphyxia

Answer 8

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) ;

Darn

Answer 9

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"

Yves

Answer 10

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/>

Predatory

Answer 11

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")))

Toweling