Writing binary data to a file, literally

Question

I have an array of integers

Array ( [0] => Array ( [0] => 1531412763 [1] => 1439959339 [2] => 76 [3] => 122 [4] => 200 [5] => 4550 [6] => 444 ) ... 

And so on, I suppose if I looked at it as if it were a database - the elements of the outermost array are the rows, and the elements of the internal arrays are the columns.

I want to save this information in a file so that I can get it later, but I want to save it as binary data to save space. Basically, if I write the first integer from example 1531412763 to a file, it will take 10 bytes, but if I could save it as a signed integer, it would take 4 bytes.

I examined a number of other answers that everyone suggests using fwrite , which I cannot figure out how to use this way?

Answer 1

You can use pack() and unpack() functions to write binary data to a file. Pack will generate a binary string. As a result of the string, you can combine ints into one string. Then write this line as a line to the file.

This way you can easily read file() , which will put the file into an array of strings. Then just unpack() each line, and you have the original array.

Something like that:

 $arr = array( array ( 1531412763, 1439959339 ), array ( 123, 456, 789 ), ); $file_w = fopen('binint', 'w+'); // Creating file content : concatenation of binary strings $bin_str = ''; foreach ($arr as $inner_array_of_int) { foreach ($inner_array_of_int as $num) { // Use of i format (integer). If you want to change format // according to the value of $num, you will have to save the // format too. $bin_str .= pack('i', $num); } $bin_str .= "\n"; } fwrite($file_w, $bin_str); fclose($file_w); // Now read and test. $lines_read will contain an array like the original. $lines_read = []; // We use file function to read the file as an array of lines. $file_r = file('binint'); // Unpack all lines foreach ($file_r as $line) { // Format is i* because we may have more than 1 int in the line // If you changed format while packing, you will have to unpack with the // corresponding same format $lines_read[] = unpack('i*', $line); } var_dump($lines_read);