For those who want a more familiar return value for the function:

<?php
function strcrc32($text) {
  $crc = crc32($text);
  if ($crc & 0x80000000) {
    $crc ^= 0xffffffff;
    $crc += 1;
    $crc = -$crc;
  }
  return $crc;
}
?>

And to show the result in Hex string:

<?php
function int32_to_hex($value) {
  $value &= 0xffffffff;
  return str_pad(strtoupper(dechex($value)), 8, "0", STR_PAD_LEFT);
}
?>