Return first key in foreach - php

Question

I have problem in returning the first key of array in foreach. I can return the $key but i cant figure out on returning the first $key only.
<td>
<div align="center">
<span class="formlist">
<select id="plant" name="plant[]" class="form-control" multiple="multiple">
<?php
$query_plant = "SELECT * FROM plant WHERE plant_enable=1 ORDER BY plant_name";
$rs_plant = DB_Query($query_plant);
while ($row_plant = DB_FetchRow($rs_plant)) {
$plant.='<option name='.$row_plant["plant_shortname"].' value='.$row_plant["plant_id"].'>' .$row_plant["plant_name"].' ['.$row_plant["plant_id"].']</option>';
}
mysql_free_result($rs_plant);
echo $plant;
?>
</select>
</span>
</div>
</td>
if(isset($_POST['plant'])) {
$checkbox1 = $_POST['plant'];
$chk="";
$stf_sql = "SELECT * FROM test_plant WHERE staff_id = '".$STAFF_ID."'";
$stf_res = DB_Query($stf_sql);
if(DB_RowsReturned($stf_res) > 0) {
$del_sql = "DELETE FROM test_plant WHERE staff_id = '".$STAFF_ID."'";
$del_res = DB_Query($del_sql);
}
foreach($checkbox1 as $chk1)
{
$in_ch="insert into test_plant(staff_id, plant_name, submit_dt) values ('$STAFF_ID','$chk1', Now())";
$in_res = DB_Query($in_ch);
$abc = mysql_query("SELECT * FROM test_plant");
while($abc_row = mysql_fetch_assoc($abc)) {
foreach($abc_row as $key => $value) {
echo $key; //return first key here
}
}
}
} else {
echo "OK";
}
I have tried returning $key[0] but it returns the first letter only. I want to return 'p_id'

Answer 1

Like this,
$keys = array_keys($checkbox1);
print_r($keys); // for all keys
echo $keys[0]; // It will echo first key of the array.

Answer 2

You could reset the internal array pointer and then get the key of the current element:
reset($checkbox1);
echo key($checkbox1);
(Put this outside your outermost while loop).
Or you could even get all the array keys, and then grab the current key:
echo current(array_keys($checkbox1));