PHP urlencode() Function: Usage, Parameters, Return Value, and Examples

The PHP urlencode() function encodes a string so it can be safely used in the query part of a URL, converting non‑alphanumeric characters (except -_. ) to percent‑encoded sequences and spaces to plus signs, matching the application/x‑www‑form‑urlencoded format.

Syntax: string urlencode(string $str) Parameter $str is the string to be encoded. The function returns the encoded string.

Example 1 demonstrates encoding user input directly within an anchor tag:

<?php
echo '<a href="mycgi?foo=' . urlencode($userinput) . '">';
?>

Example 2 builds a query string from multiple variables, encodes each part, and then safely outputs the link using htmlentities() to avoid HTML entity conflicts:

<?php
$query_string = 'foo=' . urlencode($foo) . '&bar=' . urlencode($bar);
echo '<a href="mycgi?' . htmlentities($query_string) . '">';
?>

Be cautious of variables that may contain HTML entities such as &, ©, or £ because browsers will interpret them; using htmlentities() or htmlspecialchars() is recommended.

Reference: W3C HTML4 notes on URL encoding.