Converting a PHP Array to a Query String… And Back Again

This is a scenario I have found myself in many times before; needing to convert a PHP array to a query string for use in a URL or POST request, and vice versa. Today I will discuss both methods and how they can be achieved with the aid of two very useful PHP functions; http_build_query() and parse_str().

Generating a URL query string from a PHP array

For the first part of this post let us take a look at the following PHP array:

1. $myArray = array(  
2.     "car"=>"ford",  
3.     "animal"=>"elephant",  
4.     "language"=>"php"  
5. );  

Simple enough right? Just three elements in a single-dimension array. Now lets take a look at how we can convert this to a query string using our first function http_build_query():

1. echo http_build_query($myArray);  
2.   
3. // Outputs: car=ford&animal=elephant&language=php  

How easy was that! The function also works with multi-dimensional arrays as shown below:

1. $myArray = array(  
2.     "car"=>array("ford", "vauxhall", "dodge"),  
3.     "animal"=>"elephant",  
4.     "language"=>"php"  
5. );  
6.   
7. echo http_build_query($myArray);  
8.   
9. // Outputs: car[0]=ford&car[1]=vauxhall&car[2]=dodge&animal=elephant&language=php  

We can get as simple or as complex as we like but I’ll let you play around with the function to get it working for you. Pretty useful stuff I think you’ll agree?!? Now lets look at the opposite effect of turning our query strings back into an array.

Creating a PHP array based on a query string

For this i want to refer back to the query string we generated in our first example. If you’ve forgotten it looks a little like this:

1. car=ford&animal=elephant&language=php  

It’s time to welcome our second function of today, parse_str(). Let’s put it in into action:

1. $queryString = "car=ford&animal=elephant&language=php";  
2.   
3. parse_str($queryString, $output);  
4.   
5. print_r($output);  

If done right the output will be a PHP array called $output (note the second parameter we used) containing three elements. We can see this below:

1. Array  
2. (  
3.     [car] => ford  
4.     [animal] => elephant  
5.     [language] => php  
6. )  

So there we have it. In just a couple of lines we’ve gone from an array, to a query string, and back to an array again.