crc32

crc32

Calculates the crc32 polynomial of a string

int **crc32** string $string

Generates the cyclic redundancy checksum polynomial of 32-bit lengths of the . This is usually used to validate the integrity of data being transmitted. string

Waarschuwing: > Because PHP's integer type is signed many crc32 checksums will result in negative integers on 32bit platforms. On 64bit installations all results will be positive integers though. crc32

So you need to use the "%u" formatter of  or 
 to get the string representation of the 
unsigned  checksum in decimal format.

sprintf``printf``crc32

For a hexadecimal representation of the checksum you can either use the 
"%x" formatter of  or  
or the  conversion functions, both of these
also take care of converting the  result to
an unsigned integer.

sprintf``printf``dechex``crc32

Having 64bit installations also return negative integers for higher result values was considered but would break the hexadecimal conversion as negatives would get an extra 0xFFFFFFFF######## offset then. As hexadecimal representation seems to be the most common use case we decided to not break this even if it breaks direct decimal comparisons in about 50% of the cases when moving from 32 to 64bits.

In retrospect having the function return an integer maybe wasn't the 
best idea and returning a hex string representation right away (as 
e.g.  does) might have been a better plan to
begin with.

md5

For a more portable solution you may also consider the generic 
.  will 
return the same string as .

hash``hash("crc32b", $str)``str_pad(dechex(crc32($str)), 8, '0', STR_PAD_LEFT)

stringThe data.

Returns the crc32 checksum of as an integer. string

Voorbeeld: Displaying a crc32 checksum

 This example shows how to print a converted checksum with the
  function:
`printf`

<?php
$checksum = crc32("The quick brown fox jumped over the lazy dog.");
printf("%u\n", $checksum);
?>

hash``md5``sha1