Refactor config_eval() to use PREG_SET_ORDER

Call preg_match_all() with PREG_SET_ORDER flag instead of the default
PREG_PATTERN_ORDER allows simplification of the replacement loop using
a foreach.

Assign the resulting match array elements to named variables makes the
code self-documenting and easier to read.

core/config_api.php

@@ -622,29 +622,35 @@ function env_obsolete( $p_env_variable, $p_new_env_variable ) {
 function config_eval( $p_value, $p_global = false ) {
 	$t_value = $p_value;
 	if( !empty( $t_value ) && is_string( $t_value ) && !is_numeric( $t_value ) ) {
-		if( 0 < preg_match_all( '/(?:^|[^\\\\])(%([^%]+)%)/U', $t_value, $t_matches ) ) {
-			$t_count = count( $t_matches[0] );
-			for( $i = 0;$i < $t_count;$i++ ) {
+		$t_count = preg_match_all(
+			'/(?:^|[^\\\\])(%([^%]+)%)/U',
+			$t_value,
+			$t_matches,
+			PREG_SET_ORDER
+		);
+
+		if( $t_count > 0 ) {
+			foreach( $t_matches as $t_match ) {
+				list(, $t_match_with_delimiters, $t_config ) = $t_match;
 
-				# $t_matches[0][$i] is the matched string including the delimiters
-				# $t_matches[1][$i] is the target parameter string
 				if( $p_global ) {
-					$t_repl = config_get_global( $t_matches[2][$i] );
+					$t_repl = config_get_global( $t_config );
 				} else {
-					$t_repl = config_get( $t_matches[2][$i] );
+					$t_repl = config_get( $t_config );
 				}
 
 				# Handle the simple case where there is no need to do string replace.
 				# This will resolve the case where the $t_repl value is of non-string
 				# type, e.g. array of access levels.
-				if( $t_count == 1 && $p_value == '%' . $t_matches[2][$i] . '%' ) {
+				if( $t_count == 1 && $p_value == $t_match_with_delimiters ) {
 					$t_value = $t_repl;
 					break;
 				}
 
-				$t_value = str_replace( $t_matches[1][$i], $t_repl, $t_value );
+				$t_value = str_replace( $t_match_with_delimiters, $t_repl, $t_value );
 			}
 		}
+
 		# Remove escaped '%'
 		$t_value = str_replace( '\\%', '%', $t_value );
 	}