get_preserved_comment_markers();
$html = str_replace( [ "\r\n", "\r" ], "\n", $html );
$protected_blocks = [];
$html = preg_replace_callback(
'#<(pre|code|textarea|script|style)\b[^>]*>.*?#is',
function ( array $matches ) use ( &$protected_blocks, $html ): string {
$placeholder = $this->generate_placeholder( $html, $protected_blocks );
$protected_blocks[ $placeholder ] = $matches[0];
return $placeholder;
},
$html
);
if ( $html === null ) {
return $original_html;
}
$html = preg_replace_callback(
'##s',
function ( array $matches ) use ( $preserved_comment_markers ): string {
$body = trim( $matches[1] );
if ( in_array( strtolower( $body ), $preserved_comment_markers, true ) ) {
return $matches[0];
}
if ( $this->is_conditional_comment( $body ) ) {
return $matches[0];
}
if ( $this->is_spc_debug_comment( $body ) ) {
return $matches[0];
}
return '';
},
$html
);
if ( $html === null ) {
return $original_html;
}
// Remove formatting whitespace between markup tokens, while preserving
// a single visible space between adjacent inline elements. Uses a lookahead
// for the right-hand token so chains like `\n\n` collapse on
// every gap, not just the first.
$token_alternation = '|<\/?[a-z0-9:-]+\b[^>]*>|' . self::PLACEHOLDER_PATTERN;
$html = preg_replace_callback(
'/(' . $token_alternation . ')\s+(?=(' . $token_alternation . '))/is',
function ( array $matches ): string {
if ( $this->should_preserve_inter_tag_space( $matches[1], $matches[2] ) ) {
return $matches[1] . ' ';
}
return $matches[1];
},
$html
);
if ( $html === null ) {
return $original_html;
}
if ( ! empty( $protected_blocks ) ) {
$html = strtr( $html, $protected_blocks );
}
return trim( $html );
}
/**
* Determine whether an HTML comment is a conditional comment.
*
* @param string $body Comment body without delimiters.
*
* @return bool
*/
private function is_conditional_comment( string $body ): bool {
// Downlevel-revealed openers like `` parse with body
// `[if !IE]>` close consumes the trailing `--`.
return (bool) preg_match( '/^\[if\s[^\]]+\]>.*(?:is_placeholder( $left_token ) || $this->is_placeholder( $right_token ) ) {
return false;
}
$left_tag = $this->extract_tag_name( $left_token );
$right_tag = $this->extract_tag_name( $right_token );
if ( $left_tag === null || $right_tag === null ) {
return false;
}
return in_array( $left_tag, self::INLINE_TAGS, true ) && in_array( $right_tag, self::INLINE_TAGS, true );
}
/**
* Determine whether a token is a protected-block placeholder.
*
* @param string $token Markup token.
*
* @return bool
*/
private function is_placeholder( string $token ): bool {
return (bool) preg_match( '/^' . self::PLACEHOLDER_PATTERN . '$/', $token );
}
/**
* Extract the lowercase HTML tag name from a tag token.
*
* @param string $token Markup token.
*
* @return string|null
*/
private function extract_tag_name( string $token ): ?string {
if ( preg_match( '/^<\/?\s*([a-z0-9:-]+)/i', $token, $matches ) !== 1 ) {
return null;
}
return strtolower( $matches[1] );
}
/**
* Get preserved comment markers, allowing extensions to add custom markers.
*
* @return string[]
*/
private function get_preserved_comment_markers(): array {
$markers = apply_filters( 'spc_html_minifier_preserved_comment_markers', self::PRESERVED_COMMENT_MARKERS );
if ( ! is_array( $markers ) ) {
return self::PRESERVED_COMMENT_MARKERS;
}
$markers = array_filter(
array_map(
function ( $marker ) {
return is_string( $marker ) ? strtolower( trim( $marker ) ) : '';
},
$markers
)
);
return array_values( array_unique( $markers ) );
}
/**
* Generate a collision-safe placeholder for protected blocks.
*
* @param string $html Source HTML.
* @param array $protected_blocks Existing placeholders.
*
* @return string
*/
private function generate_placeholder( string $html, array $protected_blocks ): string {
do {
$placeholder = '%%SPC_HTML_MINIFIER_BLOCK_' . md5( uniqid( '', true ) ) . '%%';
} while ( strpos( $html, $placeholder ) !== false || isset( $protected_blocks[ $placeholder ] ) );
return $placeholder;
}
}