<?php
function checkidentity($identity) {
	$id = strtoupper ( $identity );
	$regx = "/(^\d{15}$)|(^\d{17}([0-9]|X)$)/";
	$arr_split = array ();
	if (! preg_match ( $regx, $id )) 
	{
		return FALSE;
	}

	if (15 == strlen ( $id )) //检查15位  
	{
		$regx = "/^(\d{6})+(\d{2})+(\d{2})+(\d{2})+(\d{3})$/";
		@preg_match ( $regx, $id, $arr_split );
		//检查生日日期是否正确  
		$dtm_birth = "19" . $arr_split [2] . '/' . $arr_split [3] . '/' . $arr_split [4];
		if (! strtotime ( $dtm_birth )) 
		{
			return FALSE;
		} else {
			return TRUE;
		}
	} 
	else //检查18位  
	{
		$regx = "/^(\d{6})+(\d{4})+(\d{2})+(\d{2})+(\d{3})([0-9]|X)$/";
		@preg_match ( $regx, $id, $arr_split );
		$dtm_birth = $arr_split [2] . '/' . $arr_split [3] . '/' . $arr_split [4];
		if (! strtotime ( $dtm_birth )) //检查生日日期是否正确  
		{		
			return FALSE;
		} else{
			//检验18位身份证的校验码是否正确。  
			//校验位按照ISO 7064:1983.MOD 11-2的规定生成，X可以认为是数字10。  
			$arr_int = array (7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2 );
			$arr_ch = array ('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2' );
			$sign = 0;
			for($i = 0; $i < 17; $i ++) {
				$b = ( int ) $id {$i};
				$w = $arr_int [$i];
				$sign += $b * $w;
			}
			$n = $sign % 11;
			$val_num = $arr_ch [$n];
			if ($val_num != substr ( $id, 17, 1 )) {
				return FALSE;
			} else {
				return TRUE;
			}
		}
	}
}
?>