Secure SQL update in PHP - postgresql

Question

As part of a job I want to update a database using a form. Since the database is large and is used by many users, I hope that this manipulation is at least secure for more safety.
HTML script :
<form action="http://localhost/modifier_infos_signaletique.php" method=POST >
<div class="id_sign">
<h5>Id "Signalétique" :</h5>
<input type="text" name="id_sign" id="id_sign"/><br>
</div>
<h5>Infos "Signalétique" : </h5>
<input class="comment" type="text" id="maj_infos" name="maj_infos" required maxlength='140'/><br>
<input type="submit" value="Submit" />
</form>
PHP script:
<?php
$user = 'xxxx';
$pass = 'xxxx';
try{
$dbconn = new PDO('pgsql:host=localhost;port=5432;dbname=xxxx',$user, $pass);
$dbconn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$maj = $_POST['maj_infos'];
$id = $_POST['id_sign'];
$query = $dbconn->prepare("UPDATE signaletique SET infos = ':infos' WHERE id = ':id'");
$query->bindParam(':infos', $maj, PDO::PARAM_STR);
$query->bindParam(':id', $id, PDO::PARAM_INT);
$query->execute();
echo 'Données mises à jour';
}
catch(PDOException $e){
echo "Erreur : " . $e->getMessage();
}
?>
However, when I use this script this error appears:
**Erreur : SQLSTATE[HY093]: Invalid parameter number: :infos **
The error would be due to the parameter used for the bindParam function.
However, I have in the properties of my PostgreSQL database, info in "character varying". I tried to change this parameter to "text", but the error remains the same.
Forgive me for this question but I am new to PHP and my SQL skills are thin since I use pgAdmin and its tools a lot to build and interact with my databases.
Here is a screenshot of my database :
The info parameter is in "text" on the screenshot but basic this property was in "character varying" (140).
Thank you for your help.

Answer 1

In your query string you put single quotes around your placeholders. This makes them strings, not placeholders. You do not need quotes when using placeholders.
This should work:
$query = $dbconn->prepare("UPDATE signaletique SET infos = :infos WHERE id = :id");
See https://stackoverflow.com/questions/10966251/sqlstatehy093-invalid-parameter-number-parameter-was-not-defined for more information.