Enthusiastic URL encoding. URL encodes everything that's not an alphanumeric character.

enthusiasticurlencode.php

<?php

/**
 * Enthusiastically URL encode a string.
 * 
 * URL encode everything that's not an alphanumeric character.
 *
 * @author Craig Anderson <[email protected]>
 * @link https://gist.github.com/craiga/4991769#file-enthusiasticurlencode-php
 */
function enthusiasticurlencode($s, $safeCharacters = null) {
	if(is_null($safeCharacters)) {
		$safeCharacters = array();
		$zeroCharacterCode = ord("0");
		$lowercaseACharacterCode = ord("a");
		$uppercaseACharacterCode = ord("A");
		for($characterCode = $zeroCharacterCode; $characterCode < $zeroCharacterCode + 10; $characterCode++) {
			$safeCharacters[] = chr($characterCode);
		}
		for($characterCode = $lowercaseACharacterCode; $characterCode < $lowercaseACharacterCode + 26; $characterCode++) {
			$safeCharacters[] = chr($characterCode);
		}
		for($characterCode = $uppercaseACharacterCode; $characterCode < $uppercaseACharacterCode + 26; $characterCode++) {
			$safeCharacters[] = chr($characterCode);
		}
	}
	$result = "";
	$characters = str_split($s);
	foreach($characters as $character) {
		if(in_array($character, $safeCharacters)) {
			$result .= $character;
		}
		else {
			$result .= "%" . strtoupper(base_convert(ord($character), 10, 16));
		}
	}
	return $result;
}