使用PHP进行多个MYSQL更新

can someone please tell me how to modify this code so that instead of it it adding a new field to the observation table i would like it to update the table instead where the username is equal to :user and the child_ID is equal to :child_id

<?php

//load and connect to MySQL database stuff
require("config.inc.php");

if (!empty($_POST)) {
//initial query
$query = "INSERT INTO observation ( username, elg1, elg2, elg3, elg4, elg5,elg6, elg7, elg8, elg9, elg10, elg11, elg12, elg13, elg14, elg15, elg16, elg17, col1,   col2, col3, child_id ) VALUES ( :user, :elg1, :elg2, :elg3, :elg4, :elg5, :elg6, :elg7, :elg8, :elg9, :elg10, :elg11, :elg12, :elg13, :elg14, :elg15, :elg16, :elg17, :col1, :col2, :col3, :child_id )";


//Update query
$query_params = array(
    ':user' => $_POST['username'],
    ':elg1' => $_POST['elg1'],
':elg2' => $_POST['elg2'],
':elg3' => $_POST['elg3'],
':elg4' => $_POST['elg4'],
':elg5' => $_POST['elg5'],
':elg6' => $_POST['elg6'],
':elg7' => $_POST['elg7'],
':elg8' => $_POST['elg8'],
':elg9' => $_POST['elg9'],
':elg10' => $_POST['elg10'],
':elg11' => $_POST['elg11'],
':elg12' => $_POST['elg12'],
':elg13' => $_POST['elg13'],
':elg14' => $_POST['elg14'],
':elg15' => $_POST['elg15'],
':elg16' => $_POST['elg16'],
':elg17' => $_POST['elg17'],
    ':col1' => $_POST['col1'],
':col2' => $_POST['col2'],
    ':col3' => $_POST['col3'],
':child_id' => $_POST['child_id']


);

//execute query
try {
    $stmt   = $db->prepare($query);
    $result = $stmt->execute($query_params);
}
catch (PDOException $ex) {
    // For testing, you could use a die and message. 
    //die("Failed to run query: " . $ex->getMessage());

    //or just use this use this one:
    $response["success"] = 0;
    $response["message"] = "Database Error. Couldn't add post!" . $ex->getMessage();
    die(json_encode($response));
}

$response["success"] = 1;
$response["message"] = "Post Successfully Added!";
echo json_encode($response);

} else {
?>
    <h1>Add Comment</h1> 
    <form action="elg.php" method="post"> 
        Username:<br /> 
        <input type="text" name="username" placeholder="username" /> 
        <br /><br /> 
        elg1:<br /> 
        <input type="text" name="elg1" placeholder="elg1" /> 
        <br /><br />
        elg2:<br /> 
        <input type="text" name="elg2" placeholder="elg2" /> 
        <br /><br />
        elg3:<br /> 
        <input type="text" name="elg3" placeholder="elg3" /> 
        <br /><br />
        elg4:<br /> 
        <input type="text" name="elg4" placeholder="elg4" /> 
        <br /><br />
        elg5:<br /> 
        <input type="text" name="elg5" placeholder="elg5" /> 
        <br /><br />
        elg6:<br /> 
        <input type="text" name="elg6" placeholder="elg6" /> 
        <br /><br />
        elg7:<br /> 
        <input type="text" name="elg7" placeholder="elg7" /> 
        <br /><br />
        elg8:<br /> 
        <input type="text" name="elg8" placeholder="elg8" /> 
        <br /><br />
        elg9:<br /> 
        <input type="text" name="elg9" placeholder="elg9" /> 
        <br /><br />
        elg10:<br /> 
        <input type="text" name="elg10" placeholder="elg10" /> 
        <br /><br />
        elg11:<br /> 
        <input type="text" name="elg11" placeholder="elg11" /> 
        <br /><br />
        elg12:<br /> 
        <input type="text" name="elg12" placeholder="elg12" /> 
        <br /><br />
        elg13:<br /> 
        <input type="text" name="elg13" placeholder="elg13" /> 
        <br /><br />
        elg14:<br /> 
        <input type="text" name="elg14" placeholder="elg14" /> 
        <br /><br />
        elg15:<br /> 
        <input type="text" name="elg15" placeholder="elg15" /> 
        <br /><br />
        elg16:<br /> 
        <input type="text" name="elg16" placeholder="elg16" /> 
        <br /><br />
        elg17:<br /> 
        <input type="text" name="elg17" placeholder="elg17" /> 
        <br /><br />
        col1:<br /> 
        <input type="text" name="col1" placeholder="col1" /> 
        <br /><br />
        col2:<br /> 
        <input type="text" name="col2" placeholder="col2" /> 
        <br /><br />
        col3:<br /> 
        <input type="text" name="col3" placeholder="col3" /> 
        <br /><br />
        child_id:<br /> 
        <input type="text" name="child_id" placeholder="child_id" /> 
        <br /><br />




        <input type="submit" value="Add Comment" /> 
    </form> 
<?php
}

?> 

Try this:

<?php

//load and connect to MySQL database stuff
require("config.inc.php");

if (!empty($_POST)) {
//initial query
$query = "UPDATE observation SET elg1 = :elg1, elg2 = :elg2, elg3 = :elg3, elg4 = :elg4, elg5 = :elg5, elg6 = :elg6, elg7 = :elg7, elg8 = :elg8, elg9 = :elg9, elg10 = :elg10, elg11 = :elg11, elg12 = :elg12, elg13 = :elg13, elg14 = :elg14, elg15 = :elg15, elg16 = :elg16, elg17 = :elg17, col1 = :col1, col2 = :col2, col3 = :col3 WHERE username = :user AND child_id = :child_id";

//Update query
$query_params = array(
    ':user' => $_POST['username'],
    ':elg1' => $_POST['elg1'],
':elg2' => $_POST['elg2'],
':elg3' => $_POST['elg3'],
':elg4' => $_POST['elg4'],
':elg5' => $_POST['elg5'],
':elg6' => $_POST['elg6'],
':elg7' => $_POST['elg7'],
':elg8' => $_POST['elg8'],
':elg9' => $_POST['elg9'],
':elg10' => $_POST['elg10'],
':elg11' => $_POST['elg11'],
':elg12' => $_POST['elg12'],
':elg13' => $_POST['elg13'],
':elg14' => $_POST['elg14'],
':elg15' => $_POST['elg15'],
':elg16' => $_POST['elg16'],
':elg17' => $_POST['elg17'],
    ':col1' => $_POST['col1'],
':col2' => $_POST['col2'],
    ':col3' => $_POST['col3'],
':child_id' => $_POST['child_id']


);

//execute query
try {
    $stmt   = $db->prepare($query);
    $result = $stmt->execute($query_params);
}
catch (PDOException $ex) {
    // For testing, you could use a die and message. 
    //die("Failed to run query: " . $ex->getMessage());

    //or just use this use this one:
    $response["success"] = 0;
    $response["message"] = "Database Error. Couldn't add post!" . $ex->getMessage();
    die(json_encode($response));
}

$response["success"] = 1;
$response["message"] = "Post Successfully Added!";
echo json_encode($response);

} else {
?>
    <h1>Add Comment</h1> 
    <form action="elg.php" method="post"> 
        Username:<br /> 
        <input type="text" name="username" placeholder="username" /> 
        <br /><br /> 
        elg1:<br /> 
        <input type="text" name="elg1" placeholder="elg1" /> 
        <br /><br />
        elg2:<br /> 
        <input type="text" name="elg2" placeholder="elg2" /> 
        <br /><br />
        elg3:<br /> 
        <input type="text" name="elg3" placeholder="elg3" /> 
        <br /><br />
        elg4:<br /> 
        <input type="text" name="elg4" placeholder="elg4" /> 
        <br /><br />
        elg5:<br /> 
        <input type="text" name="elg5" placeholder="elg5" /> 
        <br /><br />
        elg6:<br /> 
        <input type="text" name="elg6" placeholder="elg6" /> 
        <br /><br />
        elg7:<br /> 
        <input type="text" name="elg7" placeholder="elg7" /> 
        <br /><br />
        elg8:<br /> 
        <input type="text" name="elg8" placeholder="elg8" /> 
        <br /><br />
        elg9:<br /> 
        <input type="text" name="elg9" placeholder="elg9" /> 
        <br /><br />
        elg10:<br /> 
        <input type="text" name="elg10" placeholder="elg10" /> 
        <br /><br />
        elg11:<br /> 
        <input type="text" name="elg11" placeholder="elg11" /> 
        <br /><br />
        elg12:<br /> 
        <input type="text" name="elg12" placeholder="elg12" /> 
        <br /><br />
        elg13:<br /> 
        <input type="text" name="elg13" placeholder="elg13" /> 
        <br /><br />
        elg14:<br /> 
        <input type="text" name="elg14" placeholder="elg14" /> 
        <br /><br />
        elg15:<br /> 
        <input type="text" name="elg15" placeholder="elg15" /> 
        <br /><br />
        elg16:<br /> 
        <input type="text" name="elg16" placeholder="elg16" /> 
        <br /><br />
        elg17:<br /> 
        <input type="text" name="elg17" placeholder="elg17" /> 
        <br /><br />
        col1:<br /> 
        <input type="text" name="col1" placeholder="col1" /> 
        <br /><br />
        col2:<br /> 
        <input type="text" name="col2" placeholder="col2" /> 
        <br /><br />
        col3:<br /> 
        <input type="text" name="col3" placeholder="col3" /> 
        <br /><br />
        child_id:<br /> 
        <input type="text" name="child_id" placeholder="child_id" /> 
        <br /><br />




        <input type="submit" value="Add Comment" /> 
    </form> 
<?php
}

?> 

You can essentially use the same statement. But update the syntax to an UPDATE statement.

$query = "UPDATE observation SET elg1=:elg1,elg2=:elg2,[etc] where child_id=:child_id and user=:user";