需要正确的PHP / MySQL语法帮助

Question

I've been chasing a bug all day in my code. Here's the long and short of it:

I have a variable that is passed through a query string and I want to use that variable in my MySQLi query. A-like so:

$variable;

$info = dbConnect('query');
$eInfo = "SELECT *
FROM tablename
WHERE fieldname = '$variable%'";
$eiData = $info->query($eInfo) or die(mysqli_error());
$eInfo = $eiData->fetch_assoc();

The emphasis is the % after the variable name. I'm no PHP expert but I remember picking this trick up a while back and it has worked for me on all my DB-driven websites EXCEPT the new one I'm developing.

The above query returns no data from the table.

BUT...

if I omit the % as follows:

$variable;

$info = dbConnect('query');
$eInfo = "SELECT *
FROM tablename
WHERE fieldname = '$variable'";
$eiData = $info->query($eInfo) or die(mysqli_error());
$eInfo = $eiData->fetch_assoc();

The query executes and I get my data.

WHY after writing queries where I want to use a variable using the syntax '$variable%' would this no longer work? Just dropping the % ('$variable') makes it work A-OK, which has me utterly baffled.

For what it's worth, I run a dedicated server and suPHP was recently installed, if that has any remote chance of helping make sense here (PHP 5.2.17 is my current version).

Again, I'm no PHP whiz, but after checking code form older sites I have done with MySQLi queries, the % was always there when appending a variable into a query.

I'm completely dead in the water here. Any help you can provide would be so insanely appreciated that it defies explanation.

Answer 1

如果要将变量放在难以解释变量名结尾的字符串中，请使用{$var}如下所示：

$eInfo = "SELECT * FROM tablename WHERE fieldname LIKE '{$variable}%'"; 

Answer 2

The % is a wildcard for LIKE queries. So if you use % in a query with WHERE var = 'cow%' , it's going to search the database for the literal string cow% .

1. cow
2. cows
3. cow% (match)
4. the cow

In a Like query: WHERE var LIKE 'cow%' the following will match:

1. cow (match)
2. cows (match)
3. cow% (match)
4. the cow

See MySQL Pattern Matching .