dana rockets

hello please help me how to make append the bit '1' to the message i.e. by adding 0x80 if characters are 8 bits. append 0 ≤ k < 512 bits '0', thus the resulting message length (in bits) is congruent to 448 (mod 512) append ml, in a 64-bit big-endian integer. So now the message length is a multiple of 512 bits.in PHP. please help me :Sad: