URL Encoding Quandary: When Should I Use `urlencode` vs. `rawurlencode`?

Dissecting the Differences: urlencode vs rawurlencode

When constructing a URL from a varying string, developers have two encoding options: urlencode() and rawurlencode(). This article delves into the essential distinctions between the two functions to provide guidance on their appropriate usage.

rawurlencode: A String Transformed with RFC Adherence

rawurlencode conforms to the specifications outlined in both RFC 1738 (pre-PHP 5.3.0) and RFC 3986 (post-PHP 5.3.0). It replaces non-alphanumeric characters with " " and two hexadecimal digits. This encoding method protects literal characters from misinterpretation as URL delimiters and safeguards URLs from character conversions that may occur during transmission.

urlencode: A Departure from RFC with Plus Sign Encoding

urlencode, on the other hand, departs from RFC compliance in one specific way: it encodes spaces as " " signs instead of " ," an encoding technique consistent with the posting of data from a WWW form.

When to Use Which

The appropriate choice between urlencode and rawurlencode depends on the intended purpose. If interoperability with other systems is paramount, rawurlencode emerges as the preferred option. However, for legacy systems that expect form-encoded query strings where spaces are encoded as " " rather than " ," urlencode remains the necessary choice.

RFC Nuances

It's worth noting the subtle distinction between RFC 1738 and RFC 3986 in the context of rawurlencode. Prior to PHP 5.3, rawurlencode aligned with RFC 1738, which required the encoding of the tilde character (~). However, from PHP 5.3 onwards, the function adheres to RFC 3986, which deems tilde encoding unnecessary.

Additional Considerations

RFC 2396 provides further insights into valid URI syntax. Crucially, it identifies " " as a reserved character within a query string, necessitating its encoding according to RFC 3986. Therefore, rawurlencode remains the preferred encoding method when conforming to RFC 2396.

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