How to use a php variable in mysqli?

问题:

This works

<?php

         $result = $conn->query('SELECT * FROM people
         WHERE user="55"') or die(mysql_error());  

        $row = mysqli_fetch_array( $result );
         echo $row['name'];
?>

But when I try to use a php variable, the following does not work:

<?php

     $a = 55; 
     $result = $conn->query('SELECT * FROM people
     WHERE user="$a"') or die(mysql_error());  

    $row = mysqli_fetch_array( $result );
     echo $row['name'];
?>

回答1:

Try this:

$query = 'SELECT * FROM people  WHERE user="'.$a.'"';

回答2:

You must concat the values like below

<?php $result = $conn->query('SELECT * FROM people  WHERE user="'.$a.'"') or die(mysql_error());  

    $row = mysqli_fetch_array( $result );
     echo $row['name']; ?>

回答3:

Change This: $result = $conn->query('SELECT * FROM people WHERE user="$a"') or die(mysql_error());

To This: $result = $conn->query("SELECT * FROM people WHERE user='$a'") or die(mysql_error());