Converts a number of bytes to the largest unit the bytes will fit into.

It is easier to read 1 KB than 1024 bytes and 1 MB than 1048576 bytes. Converts
number of bytes to human readable number by taking the number of that unit
that the bytes will go into it. Supports YB value.

Please note that integers in PHP are limited to 32 bits, unless they are on
64 bit architecture, then they have 64 bit size. If you need to place the
larger size then what PHP integer type will hold, then use a string. It will
be converted to a double, which should always have 64 bit length.

Technically the correct unit names for powers of 1024 are KiB, MiB etc.

function size_format( $bytes, $decimals = 0 ) {
	$quant = array(
		/* translators: Unit symbol for yottabyte. */
		_x( 'YB', 'unit symbol' ) => YB_IN_BYTES,
		/* translators: Unit symbol for zettabyte. */
		_x( 'ZB', 'unit symbol' ) => ZB_IN_BYTES,
		/* translators: Unit symbol for exabyte. */
		_x( 'EB', 'unit symbol' ) => EB_IN_BYTES,
		/* translators: Unit symbol for petabyte. */
		_x( 'PB', 'unit symbol' ) => PB_IN_BYTES,
		/* translators: Unit symbol for terabyte. */
		_x( 'TB', 'unit symbol' ) => TB_IN_BYTES,
		/* translators: Unit symbol for gigabyte. */
		_x( 'GB', 'unit symbol' ) => GB_IN_BYTES,
		/* translators: Unit symbol for megabyte. */
		_x( 'MB', 'unit symbol' ) => MB_IN_BYTES,
		/* translators: Unit symbol for kilobyte. */
		_x( 'KB', 'unit symbol' ) => KB_IN_BYTES,
		/* translators: Unit symbol for byte. */
		_x( 'B', 'unit symbol' )  => 1,
	);

	if ( 0 === $bytes ) {
		/* translators: Unit symbol for byte. */
		return number_format_i18n( 0, $decimals ) . ' ' . _x( 'B', 'unit symbol' );
	}

	foreach ( $quant as $unit => $mag ) {
		if ( (float) $bytes >= $mag ) {
			return number_format_i18n( $bytes / $mag, $decimals ) . ' ' . $unit;
		}
	}

	return false;
}