<?php
$array = array(
    array('gr_number' => 1, 'batch' => 'A', 'maths' => '80/100', 'english' => '80/100', 'science' => '80/100', 'hindi' => '80/100', 'computer' => '80/100', 'socialscience' => '85/100'),
    array('gr_number' => 2, 'batch' => 'A', 'maths' => '80/100', 'english' => '80/100', 'science' => '80/100', 'hindi' => '80/100', 'computer' => '80/100', 'socialscience' => '86/100'),
    array('gr_number' => 3, 'batch' => 'A', 'maths' => '80/100', 'english' => '80/100', 'science' => '80/100', 'hindi' => '80/100', 'computer' => '80/100', 'socialscience' => '87/100'),
);

$keys = array('gr_number', 'batch');
$excludes = array_combine($keys, array_fill(0, count($keys), 0));
$result = array_map(
    function ($arr) use($excludes) {
        $ret = array_intersect_key($arr, $excludes);
        $arr = array_diff_key($arr, $excludes);
        $ret['result_details'] = implode(', ', array_map(
            function ($v1, $v2) { return "$v1:$v2"; },
            array_keys($arr), array_values($arr)
        ));
        return $ret;
    },
    $array
);

print_r($result);