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What is the urlencode() function in PHP>|?

NDUKWE CHIDERA K.

Grokking Modern System Design Interview for Engineers & Managers

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In PHP, encoding a URL entails using urlencode() to convert a URL string into formats that are understandable by the system.

What does the urlencode() function do?

This function does the following:

  • It encodes URLs, which are basically a combination of several characters both alphanumeric and special.
  • It will convert special characters using some predefined rules and notations.
  • With the help of the urlencode() function, the encoded URL can enjoy over-the-internet transmission using the ASCII character set. This will enable our request to be successfully sent.

That notwithstanding, URLs can and do contain characters which are not part of the ASCII set. This means that such characters will be forced to a valid ASCII set.

Generally speaking, what happens here is that the URL encoding process will replace unsafe ASCII characters with a “%” followed by two hexadecimal digits, so as to safely transmit the URL. It is also important to know that a URL cannot contain spaces. If by any chance there is space in the URL, the urlencode() function will replace this space with a plus (+) or a %20. To understand this, let’s see some examples:

Syntax

string urlencode( $input )

Arguments

  • The urlencode() function needs only a single compulsory argument which is the URL string to be encoded.

Returns

  • The string that has been encoded will be returned on successful execution of the function.

Now, let’s use the code examples below to understand better.

Code 1

<?php
// let return the encoded educative.io site
$siteAddress = 'https://www.educative.io';
$encoded = urlencode($siteAddress);
echo $encoded;
?>

Explanation

In the code above, we encoded the simple address https://www.educative.io with the : and // special characters replaced, as indicated in the result with %3A and %2F%2F respectively. This kind of replacement is what happens with other special characters not recognized as part of the ASCII set.

Let’s see another example with a range of addresses, where more twists will be added.

Code 2

<?php
// let save different urls in some variables
// this will contain space
$siteAddress1 = 'https://go ogle.com';
//alot of special characters.
//This address is common in php codes underdevelopment
$siteAddress2 = 'localhost/post/user.php?id=$_POST["id"]';
// Just painting possible scenarios
$siteAddress3 = 'https://forum.com/joinforsure?orStop!(now)';
$encoded1 = urlencode($siteAddress1);
$encoded2 = urlencode($siteAddress2);
$encoded3 = urlencode($siteAddress3);
echo $encoded1;
echo $encoded2;
echo $encoded3;
?>

Why convert to ASCII?

These URLs are ASCII encoded because ASCIIAmerican Standard Code for Information Interchange provides a character set that is understood all over the world and used virtually by all platforms for data communication.

With ASCII, developers can design interfaces that both humans and computers understand. ASCII converts a string data into a character set which can be interpreted and displayed as plain text that can be read by people, and data that can be used by computers.

RELATED TAGS

php
web development
communitycreator

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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