AdventOfCode.day7.php

<?php 

$isPartTwo = true;

function def ($name, $val) {
	global $isPartTwo; 
	if ($name == "b" and $isPartTwo) $val = 956;
	eval ("function _{$name} () { static \$res; if (!\$res) \$res = {$val}; return \$res; ;}");  
};

$patterns = [
	["/^(\w+) RSHIFT (\d+) -> (\w+)$/", function ($matches) { def($matches[3], "_{$matches[1]}() >> {$matches[2]}"); }],
	["/^(\w+) LSHIFT (\d+) -> (\w+)$/", function ($matches) { def($matches[3], "_{$matches[1]}() << {$matches[2]}"); }],
	["/^(\d+) AND (\w+) -> (\w+)$/", function ($matches) { def($matches[3], "{$matches[1]} & _{$matches[2]}()"); }],
	["/^(\w+) AND (\d+) -> (\w+)$/", function ($matches) { def($matches[3], "_{$matches[1]}() & {$matches[2]}"); }],
	["/^(\w+) AND (\w+) -> (\w+)$/", function ($matches) { def($matches[3], "_{$matches[1]}() & _{$matches[2]}()"); }],
	["/^(\d+) OR (\w+) -> (\w+)$/", function ($matches) { def($matches[3], "{$matches[1]} | _{$matches[2]}()"); }],
	["/^(\w+) OR (\d+) -> (\w+)$/", function ($matches) { def($matches[3], "_{$matches[1]}() | {$matches[2]}"); }],
	["/^(\w+) OR (\w+) -> (\w+)$/", function ($matches) { def($matches[3], "_{$matches[1]}() | _{$matches[2]}()"); }],
	["/^NOT (\w+) -> (\w+)$/", function ($matches) { def($matches[2], "0xFFFF & ~_{$matches[1]}()"); }],
	["/^(\d+) -> (\w+)$/", function ($matches) { def($matches[2], $matches[1]); }],
	["/^(\w+) -> (\w+)$/", function ($matches) { def($matches[2], "_{$matches[1]}()"); }],
];

function parseLine ($line) {
    global $patterns;
    $matches = [];
    foreach ($patterns as list($pattern, $parser)) {
    	if (preg_match($pattern, $line, $matches)) {
    		$parser($matches);
    		break;
		}
    }
}
$input = [];

$handle = fopen("input.txt", "r+");
while (($line = fgets($handle)) !== false) $input[] = $line;
fclose($handle);

foreach ($input as $line) parseLine($line);

print_r(_a());