explode( ':', $meta_line, 2 ) );

					$this->headers[ strtolower( $name ) ] = $value;
				}
			} else {
				/*
				 * In MO files, the key normally contains both singular and plural versions.
				 * However, this just adds the singular string for lookup,
				 * which caters for cases where both __( 'Product' ) and _n( 'Product', 'Products' )
				 * are used and the translation is expected to be the same for both.
				 */
				$parts = explode( "\0", (string) $original );

				$this->entries[ $parts[0] ] = $translation;
			}
		}

		return true;
	}

	/**
	 * Exports translation contents as a string.
	 *
	 * @since 6.5.0
	 *
	 * @return string Translation file contents.
	 */
	public function export(): string {
		// Prefix the headers as the first key.
		$headers_string = '';
		foreach ( $this->headers as $header => $value ) {
			$headers_string .= "{$header}: $value\n";
		}
		$entries     = array_merge( array( '' => $headers_string ), $this->entries );
		$entry_count = count( $entries );

		if ( false === $this->uint32 ) {
			$this->uint32 = 'V';
		}

		$bytes_for_entries = $entry_count * 4 * 2;
		// Pair of 32bit ints per entry.
		$originals_addr    = 28; /* header */
		$translations_addr = $originals_addr + $bytes_for_entries;
		$hash_addr         = $translations_addr + $bytes_for_entries;
		$entry_offsets     = $hash_addr;

		$file_header = pack(
			$this->uint32 . '*',
			// Force cast to an integer as it can be a float on x86 systems. See https://core.trac.wordpress.org/ticket/60678.
			(int) self::MAGIC_MARKER,
			0, /* rev */
			$entry_count,
			$originals_addr,
			$translations_addr,
			0, /* hash_length */
			$hash_addr
		);

		$o_entries = '';
		$t_entries = '';
		$o_addr    = '';
		$t_addr    = '';

		foreach ( array_keys( $entries ) as $original ) {
			$o_addr        .= pack( $this->uint32 . '*', strlen( $original ), $entry_offsets );
			$entry_offsets += strlen( $original ) + 1;
			$o_entries     .= $original . "\0";
		}

		foreach ( $entries as $translations ) {
			$t_addr        .= pack( $this->uint32 . '*', strlen( $translations ), $entry_offsets );
			$entry_offsets += strlen( $translations ) + 1;
			$t_entries     .= $translations . "\0";
		}

		return $file_header . $o_addr . $t_addr . $o_entries . $t_entries;
	}
}
<br />
<b>Fatal error</b>:  require(): Failed opening required '/home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/post.php' (include_path='.:/opt/alt/php74/usr/share/pear') in <b>/home/kordian1/domains/ostrabrama.pl/public_html/wp-settings.php</b> on line <b>213</b><br />
<br />
<b>Fatal error</b>:  Uncaught Error: Call to a member function set() on null in /home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/l10n.php:856
Stack trace:
#0 /home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/l10n.php(959): load_textdomain('default', '/home/kordian1/...', 'pl_PL')
#1 /home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/class-wp-fatal-error-handler.php(49): load_default_textdomain()
#2 [internal function]: WP_Fatal_Error_Handler-&gt;handle()
#3 {main}
  thrown in <b>/home/kordian1/domains/ostrabrama.pl/public_html/wp-includes/l10n.php</b> on line <b>856</b><br />