<?php
$input='1+2=';
function calc
($char=substr($input,$i=0,1),$arr=[],$signArr=[],$mem=0) {
$mem.=$char;
} else {
$mem=NULL;
}
return calc
(substr($input,$i++,1),$arr,$signArr,$mem); }
if ($signArr[0]=='+') {
$arr[0]=$arr[0] + $arr[1];
$signArr[0]=$signArr[1];
return calc
(substr($input,$i++,1),$arr,$signArr,$mem); }
}
return $arr[0];
}
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