Polish up and add some docs

src/helpers/class-xml-character-filter.php

@@ -1,47 +1,72 @@
 <?php
-
-/*
- * String which will be prefixed to stream URLs to add this filter
+/**
+ * XML_Character_Filter file.
+ *
+ * @package WordPress
+ * @subpackage Importer
  */
+
+// String which will be prefixed to stream URLs to add this filter.
 define( 'XML_CHARACTER_FILTER_PREFIX', 'php://filter/read=xml_character_filter/resource=' );
 
 /**
- * Class XML_Character_Filter 
+ * Class XML_Character_Filter.
  *
- * Filter for PHP stream
- *
- * Remove control characters except newline, tab and return
+ * XML Character Stream Filter to sanitize XML input. Removes control characters except newline, tab and return.
  *
  * Usage: php://filter/read=xml_character_filter/resource=zip://archive.zip#import.xml;
  */
 class XML_Character_Filter extends php_user_filter {
+	/**
+	 * List of control characters to remove.
+	 *
+	 * @var array
+	 */
+	private $chars = array();
 
-	private $chars = [];
-
+	/**
+	 * This method is called whenever data is read from or written to the attached stream (such as with fread() or fwrite()).
+	 *
+	 * @param resource $in       A resource pointing to a bucket brigade which contains one or more bucket objects containing data to be filtered.
+	 * @param resource $out      A resource pointing to a second bucket brigade into which the modified buckets should be placed.
+	 * @param int      $consumed Reference to the length of the data that the filter reads in and alters.
+	 * @param bool     $closing  Whether the stream is in the process of closing.
+	 * @return int PSFS_PASS_ON|PSFS_FEED_ME|PSFS_ERR_FATAL.
+	 */
 	public function filter( $in, $out, &$consumed, $closing ) {
-		while ( $bucket = stream_bucket_make_writeable( $in ) ) {
-			$consumed     += $bucket->datalen;
+		while ( $bucket = stream_bucket_make_writeable( $in ) ) { //phpcs:ignore WordPress.CodeAnalysis.AssignmentInCondition
+			$consumed    += $bucket->datalen;
 			$bucket->data = $this->replace_chars( $bucket->data );
 			stream_bucket_append( $out, $bucket );
 		}
 
 		return PSFS_PASS_ON;
 	}
 
-	private function replace_chars( $string ) {
-		return str_replace( $this->chars, ' ', $string );
-	}
-
+	/**
+	 * This method is called during instantiation of the filter class object.
+	 *
+	 * @return bool
+	 */
 	public function onCreate() {
-		for ( $ascii_num = 0; $ascii_num < 32; $ascii_num ++ ) {
-			if ( $ascii_num !== 9 && $ascii_num !== 10 && $ascii_num !== 13 ) {
+		for ( $ascii_num = 0; $ascii_num < 32; $ascii_num++ ) {
+			if ( 9 !== $ascii_num && 10 !== $ascii_num && 13 !== $ascii_num ) {
 				$this->chars[] = chr( $ascii_num );
 			}
 		}
 		$this->chars[] = chr( 127 );
 
 		return true;
 	}
-}
 
+	/**
+	 * Replace control characters.
+	 *
+	 * @param string $string Data to replace.
+	 * @return string
+	 */
+	private function replace_chars( $string ) {
+		return str_replace( $this->chars, ' ', $string );
+	}
+}
 stream_filter_register( 'xml_character_filter', 'XML_Character_Filter' );