A valid SQL-command won't run in PHP

I ran the following code in PHPAdmin's terminal:

SELECT COUNT( * )
FROM User
WHERE email = 'ijp' 

and got result 0.

Then part of my PHP pro开发者_运维问答gram goes as follows:

$email = clean_input($_POST['email']);
$query = "SELECT COUNT(*) FROM user WHERE '.$email.'=email"; 
echo $query;
$result = mysqli_query($link, $query);
echo $result;
mysqli_close($link);

I have checked that I logging into the database went fine. Still the output is

SELECT COUNT(*) FROM User WHERE email='ijp'
Catchable fatal error: Object of class mysqli_result could not be converted to string   in .../html/register.php on line 49

How can I run MySQL-commands in PHP?

You are passing the $result resource to echo which expects a string. You need to use one of the mysqli_fetch_* functions to read the value from the $result and then print it.

mysqli_fetch() is deprecated, use mysqli_fetch_array or mysql_fetch_assoc or mysql_fetch_all, for example:

$row = mysqli_fetch_array($result);
if($row) {
    echo $row[0];
}

Try using

$query = "SELECT COUNT(*) FROM user WHERE email=\"".$email."\"";

If the value or $email is 'ijp', the value of $query after

$query = "SELECT COUNT(*) FROM user WHERE '.$email.'=email"; 

Would be...

SELECT COUNT(*) FROM user WHERE ijp=email

Use '$email' instead of '.$email.'

all the above answers are all correct but one thing was ommited... you need to differentiate between a table called "User" and one called "user" - they are case-sensitive on *NIX systems (Linux and the like)