PHP: Generate an alpha-numeric password salt

<?php
/**
 * This function generates an alpha-numeric password salt (with a default of 32 characters)
 * @param $max integer The number of characters in the string
 *
 */
function generateSalt($max = 32) {
$baseStr = time() . rand(0, 1000000) . rand(0, 1000000);
$md5Hash = md5($baseStr);
if($max < 32){
$md5Hash = substr($md5Hash, 0, $max);
}
return $md5Hash;
}

//Usage:
/*
echo "Salt with 32 characters:\n";
echo generateSalt() . "\n";
echo "Salt with 5 characters:\n";
echo generateSalt(5) . "\n";
*/
?>