Source

File: wp-includes/class-wp-oembed.php

public function _strip_newlines( $html, $data, $url ) {
		if ( false === strpos( $html, "\n" ) ) {
			return $html;
		}

		$count     = 1;
		$found     = array();
		$token     = '__PRE__';
		$search    = array( "\t", "\n", "\r", ' ' );
		$replace   = array( '__TAB__', '__NL__', '__CR__', '__SPACE__' );
		$tokenized = str_replace( $search, $replace, $html );

		preg_match_all( '#(<pre[^>]*>.+?</pre>)#i', $tokenized, $matches, PREG_SET_ORDER );
		foreach ( $matches as $i => $match ) {
			$tag_html  = str_replace( $replace, $search, $match[0] );
			$tag_token = $token . $i;

			$found[ $tag_token ] = $tag_html;
			$html                = str_replace( $tag_html, $tag_token, $html, $count );
		}

		$replaced = str_replace( $replace, $search, $html );
		$stripped = str_replace( array( "\r\n", "\n" ), '', $replaced );
		$pre      = array_values( $found );
		$tokens   = array_keys( $found );

		return str_replace( $tokens, $pre, $stripped );
	}