The urlencode() function is used to encode strings into URL-safe formats, where non-alphanumeric characters (except -, _, and .) are replaced with a percent sign followed by a two-digit hexadecimal number. For example, spaces are converted to signs, exclamation marks are converted to!, and Chinese characters are converted to their UTF-8 encoding form. When using, only the parameter values ??should be encoded, not the entire URL, to avoid damaging the URL structure. For other parts of the URL, such as path segments, the rawurlencode() function should be used, which converts the space to. When processing array parameters, you can use http_build_query() to automatically encode, or manually call urlencode() on each value to ensure safe transfer of data. It is key to correctly selecting functions and applying them on demand.
When you need to encode a string for use in a URL using PHP, urlencode() is the go-to function. It converts special characters into their percent-encoded representations, making sure your data is transmitted correctly over HTTP.
What does urlencode() do?
This function takes a string and returns a new string where all non-alphanumeric characters (except - , _ , and . ) are replaced with a % followed by two hexadecimal digits. For example, spaces become , and Chinese characters get converted into their UTF-8 encoded form like你.
If you're building query strings manually or passing dynamic values ??in URLs, this encoding is essential to avoid breaking the URL structure.
How to use urlencode() – basic examples
Here's how it works in practice:
echo urlencode("Hello World!"); // Outputs: Hello World! Notice that the space becomes a plus sign ( ) and the exclamation mark becomes ! . This behavior follows the application/x-www-form-urlencoded MIME type rules.
You might commonly use it when constructing URLs with GET parameters:
$title = "My awesome blog post!"; $url = "https://example.com/blog?title=" . urlencode($title); // Resulting URL: https://example.com/blog?title=My awesome blog post!
Some key points:
- Always apply
urlencode()to individual parameter values, not the full URL. - Don't encode the entire URL — that would mess up the structure (like turning
?into?). - Use it before appending values ??to query strings.
When to use rawurlencode() instead
There's also a similar function called rawurlencode() . The main difference is that rawurlencode() follows RFC 3986 and encodes the space character as Instead of .
So if you're working with parts of a URL other than query strings (eg, path segments), rawurlencode() may be more appropriate:
echo rawurlencode("Hello World!"); // Outputs: Hello World!Use these guidelines to choose between them:
- Use
urlencode()for query string parameters. - Use
rawurlencode()for encoding URI components like paths or slugs.
Handling arrays and multiple parameters
PHP can automatically handle array-style query parameters when building URLs:
$params = ['color' => 'blue', 'size' => ['large', 'medium']]; echo http_build_query($params); // Outputs: color=blue&size[0]=large&size[1]=medium
But if you're doing it manually and want to encode each value yourself, still use urlencode() :
$values ??= ['red', 'green', 'blue'];
foreach ($values ??as $value) {
$query .= '&color[]=' . urlencode($value);
}This gives you more control while ensuring safe encoding.
Basically that's it. It is not a big problem to use the functions, distinguish the scene, and do not encode the entire URL in advance.
The above is the detailed content of How to URL encode a string in PHP with urlencode. For more information, please follow other related articles on the PHP Chinese website!
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