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How do I convert an int to byte array in PHP?

Posted on 2010-08-25
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Last Modified: 2012-05-10
I need to convert an integer value to a 2 byte array and then to a 2 character string to write to a text file.  I obtain the value from the file using:

$fhandle = fopen($this->FilePath, 'r');
$myVal  = unpack('S',fread($fhandle, 2));
echo 'My Val = '.$myVal[1]; //let's say that $myVal = 1234

How do I convert the value back to the original format from an integer?

Thank you,

j
0
Comment
Question by:j-tech
2 Comments
 
LVL 3

Accepted Solution

by:
Mathias earned 500 total points
ID: 33528511
Take a look at this:

Output:
----------
0x1234
LB: 0x34
HB: 0x12
0x1234
LB: 0x34
HB: 0x12
0x12345678LW: 0x5678
HW: 0x1234
0x12345678LW: 0x5678
HW: 0x1234
Start: 0x1234
Array: 0x34, 0x12,
Array: 52, 18
String: 4
Hex output
34 12                                           | 4.
----------
<?php

// Function found at: http://www.theserverpages.com/scripts/

// Please leave this comment intact when using this code!

function hexoutput($data, $width=16)

{

	$st=0;

	$txt="";

	$out="";

	for ($i=0; $i<strlen($data); $i++)

	{

		$n=ord(substr($data,$i,1));

		$c=str_pad(dechex($n),2,"0",STR_PAD_LEFT);

		$out.=$c." ";

		if ($n==32 || $n>32 && $n<127 || $n>160)

		{

			$txt.=substr($data,$i,1);

		}

		else

		{

			$txt.=".";

		}

		if ($i % $width == $width-1)

		{

			$out.="| ".$txt."\n";

			$txt="";

		}

	}

	$out.=str_repeat("   ",$width-($i % $width));

	$out.="| ".$txt;

	$out.="\n";

	return $out;

}



function LO_BYTE($x)

{

	return ($x & 0x00FF);

}

function HI_BYTE($x)

{

	return (($x & 0xFF00) >> 8);

}

function LO_WORD($x)

{

	return ($x & 0xFFFF);

}

function HI_WORD($x)

{

	return (($x >> 16) & 0xFFFF);

}

function MAKE_WORD($a, $b)

{

	return (($b << 8) + $a);

}

function MAKE_LONG($a, $b)

{

	return ($a | ($b << 16));

}



echo '<pre>';



$test = 0x1234;

echo sprintf("0x%04X\n", $test);



echo sprintf("LB: 0x%02X\n", LO_BYTE($test));

echo sprintf("HB: 0x%02X\n", HI_BYTE($test));



$test = MAKE_WORD(LO_BYTE($test), HI_BYTE($test));

echo sprintf("0x%04X\n", $test);



echo sprintf("LB: 0x%02X\n", LO_BYTE($test));

echo sprintf("HB: 0x%02X\n", HI_BYTE($test));



$test = 0x12345678;

echo sprintf("0x%08X", $test);



echo sprintf("LW: 0x%04X\n", LO_WORD($test));

echo sprintf("HW: 0x%04X\n", HI_WORD($test));



$test = MAKE_LONG(LO_WORD($test), HI_WORD($test));

echo sprintf("0x%04X", $test);



echo sprintf("LW: 0x%04X\n", LO_WORD($test));

echo sprintf("HW: 0x%04X\n", HI_WORD($test));



$test = 0x1234;

echo sprintf("Start: 0x%04X\n", $test);

echo "Array: ";

$arr = array(LO_BYTE($test), HI_BYTE($test));

foreach ($arr as $a)

	echo sprintf("0x%02X, ", $a);

echo "\n";

echo "Array: ".implode(", ", $arr)."\n";

echo "String: ";

$str = '';

foreach ($arr as $a)

{

	$str .= sprintf("%c", $a);

}

echo $str."\n";

echo "Hex output\n";

echo hexoutput($str);



echo '</pre>';

?>

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Author Comment

by:j-tech
ID: 33533377
Thanks TDS, that worked perfectly.  Also helped with converting an integer to a single byte array to single character string.  Appreciate it!
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