Objective C uint8_t PHP equivalent

Question

I am converting small Objective C code in PHP script to convert integer array to Binary File.

Objective C code

typedef struct {
    uint8_t fj1;
    uint8_t fj2;
    uint8_t sr1;
    uint8_t sr2;
    uint8_t zh1;
    uint8_t zh2;
    uint8_t as1;
    uint8_t as2;
    uint8_t mg1;
    uint8_t mg2;
    uint8_t is1;
    uint8_t is2;
    
} struct_pt;

struct_pt g_p_t[366]= {
    1, 29, 2, 49, 8, 15, 11, 16, 13, 37, 14, 52,
    1, 29, 2, 49, 8, 16, 11, 17, 13, 37, 14, 53,
    1, 29, 2, 50, 8, 16, 11, 18, 13, 38, 14, 53,
…………..
    }

const char *filePath = "/Users/usr/path/to/folder/filename.bin”;

FILE *file = fopen(filePath, "wb");

if (file != NULL) {
        fwrite(g_p_t, sizeof(uint8_t), sizeof(g_p_t), file);
}

And here is my PHP Code

// array of 366 rows
$arr = [1, 29, 2, 49, 8, 15, 11, 16, 13, 37, 14, 52,
1, 29, 2, 49, 8, 16, 11, 17, 13, 37, 14, 53,
1, 29, 2, 50, 8, 16, 11, 18, 13, 38, 14, 53,
……..
];

header("Content-Disposition: attachment; filename=\”file.bin\"");
header("Pragma: no-cache");
header("Expires: 0");


    for ($i=0; $i < count($arr); $i++) { 
        echo trim(pack("I", $arr[$i]));
    }


fclose($out);

?>

The Binary File generated by PHP is a bit different from the file generated by Obj-C. I suppose I need to do character encoding in PHP.

Can you please guide me what is the equivalent encoding of uint8_t in PHP?

Answer 1

Found the solution.

PHP pack() packs the data into Binary string by taking format parameter.

As I am using "I" -> unsigned integer in pack() give result of 32bit encoding. Then trim() removes extra spaces and resulting data become encoding of below 8bit.

I've tried to generate a single-byte string from a number by using chr() in PHP

echo chr($arr[$i]);

And it worked for me :).