PDO update same value [duplicate] - php

Question

The code I've written so far works fine if there is only one named place holder for a prepared statement but if there are multiple conditions for a query, it doesn't return any results from the database.
For instance:
$query = array();
$query['columns'] = array('*');
$query['tables'] = array('esl_comments');
$query['where'] = array(
'esl_comments.commentVisible' => array('=', 'Y')
);
Works fine. But if I try:
$query = array();
$query['columns'] = array('*');
$query['tables'] = array('esl_comments');
$query['where'] = array(
'esl_comments.commentVisible' => array('=', 'Y'),
'esl_comments.commentID' => array('=', '1'),
);
(Note the additional commentID parameter) it fails to return anything despite there being data in the mySQL database that satisfies the conditions.
The PDO code i've written is:
$sql ='SELECT ';
foreach($query['columns'] as $column){ //What columnns do we want to fetch?
$sql.=$column . ", ";
}
$sql = rtrim($sql, " ,");
$sql .=' FROM '; //Which tables will we be accessing?
foreach($query['tables'] as $tables){
$sql.=$tables . ", ";
}
$sql = rtrim($sql, " ,"); //Get rid of the last comma
$sql .=' WHERE ';
if(array_key_exists('where', $query)) //check if a where clause was provided
{
$fieldnames = array_keys($query['where']);
$count = 0;
$size = sizeof($fieldnames);
$bindings = array();
foreach($query['where'] as $where){
$cleanPlaceholder = str_replace("_", "", $fieldnames[$count]);
$cleanPlaceholder = str_replace(".", "", $cleanPlaceholder);
$sql.=$fieldnames[$count].$where[0].":".$cleanPlaceholder." AND ";
$bindings[$cleanPlaceholder]=$where[1];
$count++;
}
$sql = substr($sql, 0, -5); //Remove the last AND
}
else{ //no where clause so set it to an always true check
$sql.='1=1';
$bindings=array('1'=>'1'); //Provide default bindings for the statement
}
$sql .= ';'; //Add the semi-colon to note the end of the query
echo $sql . "<br/><br/>";
// exit();
$stmt = $this->_connection->prepare($sql);
foreach($bindings as $placeholder=>$bound){
echo $placeholder . " - " . $bound."<br/>";
$stmt->bindParam($placeholder, $bound);
}
$result = $stmt->execute();
echo $stmt->rowCount() . " records<br/>";
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);
I'm building queries dynamically and therefore I am cleaning the placeholders, by stripping them of periods and underscores - hence the use of the 'cleanPlaceholder' variable.
The query being generated looks like this:
SELECT * FROM esl_comments WHERE esl_comments.commentVisible=:eslcommentscommentVisible AND esl_comments.commentID=:eslcommentscommentID;
And the parameters being bound look like this:
eslcommentscommentVisible - Y
eslcommentscommentID - 1

Answer 1

bindParam Requires a reference
The problem is caused by the way you bind parameters in the foreach loop.
foreach($bindings as $placeholder=>$bound){
echo $placeholder . " - " . $bound."<br/>";
$stmt->bindParam($placeholder, $bound);
}
bindParam requires a reference. It binds the variable, not the value, to the statement. Since the variable in a foreach loop is reset at the start of each iteration, only the last reference to $bound is left intact, and you end up binding all your placeholders to it.
That's why your code works when $query['where'] contains only one entry, but fails when it contains more than one.
You can solve the problem in 2 ways:
Pass by reference
foreach($bindings as $placeholder => &$bound) { //pass $bound as a reference (&)
$stmt->bindParam($placeholder, $bound); // bind the variable to the statement
}
Pass by value
Use bindValue instead of bindParam:
foreach($bindings as $placeholder => $bound) {
$stmt->bindValue($placeholder, $bound); // bind the value to the statement
}