PHP的源码和前面发 的那个JAVA的RC4加密基本连参数都是一样的，PHP加密后两边都可以直接解密。

源码:

<?php
function rc4($key_str, $data_str) {
	// convert input string(s) to array(s)
	$key = array ();
	$data = array ();
	for($i = 0; $i < strlen ( $key_str ); $i ++) {
		$key [] = ord ( $key_str {$i} );
	}
	for($i = 0; $i < strlen ( $data_str ); $i ++) {
		$data [] = ord ( $data_str {$i} );
	}
	// prepare key
	$state = array (
		0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,
		16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,
		32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,
		48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,
		64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,
		80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,
		96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,
		112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,
		128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,
		144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,
		160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,
		176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,
		192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,
		208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,
		224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,
		240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255
	);
	$len = count ( $key );
	$index1 = $index2 = 0;
	for($counter = 0; $counter < 256; $counter ++) {
		$index2 = ($key [$index1] + $state [$counter] + $index2) % 256;
		$tmp = $state [$counter];
		$state [$counter] = $state [$index2];
		$state [$index2] = $tmp;
		$index1 = ($index1 + 1) % $len;
	}
	// rc4
	$len = count ( $data );
	$x = $y = 0;
	for($counter = 0; $counter < $len; $counter ++) {
		$x = ($x + 1) % 256;
		$y = ($state [$x] + $y) % 256;
		$tmp = $state [$x];
		$state [$x] = $state [$y];
		$state [$y] = $tmp;
		$data [$counter] ^= $state [($state [$x] + $state [$y]) % 256];
	}
	// convert output back to a string
	$data_str = "";
	for($i = 0; $i < $len; $i ++) {
		$data_str .= chr ( $data [$i] );
		//echo $data_str."---".$data [$i]."\r\n";
	}
	return $data_str;
}
?>