获取例如aAAAxAAAa里的x规则的PHP方法,，另解.

<?php
$starttime = microtime(true);
$arr = range('a','z');
$str = file_get_contents("input.txt");
$len = strlen($str);
$x = str_split($str);
$ss = array();
foreach($arr as $va){	//循环a~z
	$d = array_keys($x,$va);
	foreach($d as $va){
		$ex1 = $va+1;
		$ex2 = $va+2;
		$ex3 = $va+3;
		$ex4 = $va+4;
		if($ex1 < $len){
			$a1 = in_array($x[$ex1],$arr);
			if($a1 === true){
				continue;
			}
		}else{
			continue;
		}
		if($ex2 <	$len){
			$a2 = in_array($x[$ex2],$arr);
			if($a2 === true){
				continue;
			}
		}else{
			continue;
		}
		if($ex3 <	$len){
			$a3 = in_array($x[$ex3],$arr);
			if($a3 === true){
				continue;
			}
		}else{
			continue;
		}
		if($ex4 <	$len){
			$a4 = in_array($x[$ex4],$arr);
			if($a4 === false){
				continue;
			}
		}else{
			$a4 = true;
		}
		$es1 = $va-1;
		$es2 = $va-2;
		$es3 = $va-3;
		$es4 = $va-4;
		if(	$es4  >= 0){
			$b4 = in_array($x[$es4],$arr);
			if($b4 === false){
				continue;
			}
		}else{
			$b4 = true;
		}
		if($es3 >= 0){
			$b3 = in_array($x[$es3],$arr);
			if($b3 === true){
				continue;
			}
			
		}else{
			continue;
		}
		if($es2 >= 0){
			$b2 = in_array($x[$es2],$arr);
			if($b2 === true){
				continue;
			}
		}else{
			continue;
		}
		if($es1 >= 0){
			$b1 = in_array($x[$es1],$arr);
			if($b1 === true){
				continue;
			}
		}else{
			continue;
		}
		if($a1 === false && $a2 === false && $a3=== false	&& $a4 === true && $b1 === false && $b2 === false && $b3 === false	&& $b4 === true){
			$ss[$va] = $x[$va];
		}
	}
}
ksort($ss);
echo implode($ss);
$end = microtime(true);
echo '<hr>',$end - $starttime;