php str_pad() fills the string into a string of specified length_PHP tutorial

/**
* Fill the string into a string of specified length (multi-byte safe)
* @param string $str specifies the filled string
* @param int $len specifies the filled string The length, if the value is negative or less than the length of the string, it will not be filled
* @param string $pad_str The string to be filled
* @param int $pad_type specifies the direction of filling STR_PAD_RIGHT, STR_PAD_LEFT or STR_PAD_BOTH
* @return string
*/

// string str_pad(string $str, int $len, string $pad_str, string $pad_type);

echo str_pad($result2[0] ,6,"0",STR_PAD_LEFT);