PHP While语句显示与queryresult相同的结果

Question

I'm having a little bit of trouble with my PHP function. In the database I get 2 results back from my query. But my function is doing something else. It changes when I edit '=' to '=='

MySQL Query:

SELECT ContentPages.ContentPagesID, ContentType.ContentTypeName
FROM `ContentPages` INNER JOIN ContentType ON ContentPages.ContentTypeID = ContentType.ContentTypeID INNER JOIN ContentInformation ON ContentPages.ContentInformationID = ContentInformation.ContentInformationID

Result:

ContentPagesID                  ContentTypeName
01425d4a-2abd-11e4-b991-525400  products01
014269dd-2abd-11e4-b991-525400  information01

PHP Function:

function GetAllPages() {
$GetAllPagesSql = "SELECT ContentPages.ContentPagesID, ContentType.ContentTypeName FROM `ContentPages` INNER JOIN ContentType ON ContentPages.ContentTypeID = ContentType.ContentTypeID INNER JOIN ContentInformation ON ContentPages.ContentInformationID = ContentInformation.ContentInformationID";
    $GetAllPagesQuery = mysql_query($GetAllPagesSql);
    while (($GetAllPagesRow = \mysql_fetch_array($GetAllPagesQuery)) != false) {
        if($GetAllPagesRow[ContentTypeName] === 'product01') {
            DisplayProducts01DesignFunction();
        }
        else if ($GetAllPagesRow[ContentTypeName] === 'information01') {
            DisplayInformation01DesignFunction();
        }
    }
}

When I change:

if($GetAllPagesRow[ContentTypeName] = 'product01') {
    DisplayProducts01DesignFunction();
}
else if ($GetAllPagesRow[ContentTypeName] = 'information01') {
    DisplayInformation01DesignFunction();
}

To this:

if($GetAllPagesRow[ContentTypeName] === 'product01') {
    DisplayProducts01DesignFunction();
}
else if ($GetAllPagesRow[ContentTypeName] === 'information01') {
    DisplayInformation01DesignFunction();
}

It goes from showing function DisplayProducts01DesignFunction() twice to DisplayInformation01DesignFunction() once.

Any ideas on how to fix this?

Answer 1

It should actually be running it only once if your code is fixed. When you change that == to = that then doesn't remain a comparison and becomes an assignment which results to TRUE and hence your if block gets executed, which is wrong.

if($GetAllPagesRow[ContentTypeName] = 'product01')

Is not the correct way to write an if condition, if you are making your code run fine using that logic then you're doing it wrong. That = should be ==

When you say

if($GetAllPagesRow[ContentTypeName] = 'product01')

Then that if block will always be executed even if you have 100 rows.

Now you might ask ok when I put == then why doesn't the first if block work anymore? Its because you are comparing a wrong string, your database contains products01 and your if contains product01, see the missing s. Your actual if condition should be

if($GetAllPagesRow[ContentTypeName] == 'products01') {
    DisplayProducts01DesignFunction();
}
else if ($GetAllPagesRow[ContentTypeName] == 'information01') {
    DisplayInformation01DesignFunction();
}