在PHP中从嵌套的foreach中删除数组值

Question

I am essentially trying to compare Array1, with Array2, to find matching rows. However, both arrays have around 14000 rows (from sql table), so I figured it would be logical to delete matching rows in array2 once found, to reduce the number of iterations overall.

It looks something like this:

foreach($array1 as $arrayRow){
    foreach($array2 as $array2Row){
        if($arrayRow['ID'] == $array2Row['ID']{
         $matchfound = 1;
         unset($array2,$array2Row);
        }
    }
}

However seemingly, nothing happens at all when running the above code.

Note: The data for array 1 and 2 come from two separate databases, and I am unable to run a query on both at once (hence having to do this in php)

Answer 1

It appears that code will unset $array2 itself, and the local copy of the row within your loop ($array2Row). Instead, get the key for the row you want to unset, and unset the entry directly:

foreach($array1 as $arrayRow){
    foreach($array2 as $key => $array2Row){
        if($arrayRow['ID'] == $array2Row['ID']{
           $matchfound = 1;
           unset($array2[$key]);
        }
    }
}