Update sql table of only rows where checkbox is checked php - php

Question

I have a table of values that I am trying to update only the date of. I have a checkbox that I want only the select rows to updated when its checked and user clicks the submit button. The issue I am having is let's say I have 4 records and I only want record 1,2 and 4 updated. What is happening is records 1,2 and 3 are being updated. I know it has something to do with the array in the foreach loop. Side note I know the sql code allows for injection I am trying to get this to work first before worrying about that. Thank you for any and all help and time.
Table Code
$sql = "SELECT * FROM tblUnitMaster WHERE JobNumber = '" . $JobNumber . "' AND `EngReleaseDate` IS NULL OR `EngReleaseDate` = '' ORDER BY UnitID";
$result=$conn->query($sql);
echo "<style>";
echo "th {";
echo "background-color: #6EB4FF;";
echo "color: white;";
echo "}";
echo "</style>";
echo "<form action=pmReleaseEngineering3.php method=post>";
echo "<input type=hidden name=JobNumber value=$JobNumber />";
echo "<table border=2 cellpadding=4 cellspacing=10>";
echo "<tr>";
echo "<th><b><font size=4></font></b></th>";
echo "<th><b><font size=4>"."Job"."</font></b></th>";
echo "<th><b><font size=4>"."Code"."</font></b></th>";
echo "<th><b><font size=4>"."Model Number"."</font><?b></th>";
echo "<th><b><font size=4>"."Serial Number"."</font><?b></th>";
echo "<th><b><font size=4>"."Scope"."</font></b></th>";
echo "<th><b><font size=4>"."Date"."</font></b></th>";
echo "</tr>";
while ($row=$result->fetch_array())
{
echo "<tr>";
//echo "<td><font color=silver size=4>".$row[0]."</font></td>"; // Unit Number
echo "<td><input type=checkbox name=check[] value=".$row[0]." checked></td>";
echo "<td><input name=UnitID type=text font color=silver size=3 value=".$row[0]." readonly/></td>"; // Unit Number
echo "<td><font color=silver size=4>".$row[5]."</font></td>"; // Job Code
echo "<td><font color=silver size=4>".$row[2]."</font></td>"; // Model Number
echo "<td><font color=silver size=4>".$row[3]."</font></td>"; // Serial Number
echo "<td><font color=silver size=4>".$row[4]."</font></td>"; // Scope
echo "<td><input name=EngReleaseDate size=6 type=datetime value=" . date('Y-m-d'). " /></td>";
echo "</tr>";
}
echo "</table>";
echo "<br>";
echo "<button class=button style=vertical-align:middle><span>Submit</span></button>";
echo "</form>";
echo "<br>";
PHP SQL Update TBL Code
include('pmconnect.php');
$JobNumber=$_REQUEST['JobNumber']; //array
$UnitID=$_POST['UnitID']; // array
$EngReleaseDate=$_POST['EngReleaseDate']; // array
if(isset($_POST['check'])){
//if(!empty($_POST['check'])) {
foreach($_POST['check'] as $a => $B){
$sql = "UPDATE tblUnitMaster SET " .
"EngReleaseDate='" . $EngReleaseDate . "'" .
"WHERE UnitID='" . $UnitID . "'";
//$result=$conn->query($sql);
if ($conn->multi_query($sql) === TRUE)
echo "<table border=1 cellpadding=4 cellspacing=10>";
echo "<tbody>";
echo "<tr>";
echo "<td><b><font size=4>Unit ID</font></b></td>";
echo "<td><b><font size=4>Eng. Release</font></b></td>";
echo "</tr>";
echo "<tr>";
echo "<td><font size=4> $UnitID </font></td>";
echo "<td><font size=4> $EngReleaseDate </font></td>";
echo "</tr>";
echo "</tbody>";
echo "</table>";
echo"<br>";
}
}