需要帮助将默认文本值插入mysql(need help inserting a default text value into mysql)

 结束网络开发人员，我从另一个团队完成了CMS，我必须与我的前端链接。 我做了一些修改，但由于我缺乏PHP知识，我在这里有一些问题。 
 
 我的用户可以填写表单，其中1个文本字段要求他们的照片链接。 我想检查输入的值是否不等于我想要的，然后我将查询插入一个默认的头像照片链接到mysql进行处理。 
 
 我在php上试过的代码 
 
// check if the variable $photo is empty, if it is, insert the default image link
if($photo = ""){
    $photo="images/avatarDefault.png";
}
 
 似乎没有用 
 
<?php
if($_SERVER["REQUEST_METHOD"] === "POST")
{
    //Used to establish connection with the database
    include 'dbAuthen.php';
    if (mysqli_connect_errno())
    {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }
    else
    {

        //Used to Validate User input
        $valid = true;

        //Getting Data from the POST
        $username = sanitizeInput($_POST['username']);
        $displayname = sanitizeInput($_POST['displayname']);
        $password = sanitizeInput($_POST['password']);

        //hash the password using Bcrypt - this is to prevent 
        //incompatibility from using PASSWORD_DEFAULT when the default PHP hashing algorithm is changed from bcrypt  
        $hashed_password = password_hash($password, PASSWORD_BCRYPT);

        //Determining Type of the User
        //if B - User is student
        //if A - User is adin
        if($_POST['type'] == 'true')
            $type = 'B';
        else
            $type = 'A';

        $email = sanitizeInput($_POST['email']);
        $tutorGroup = sanitizeInput($_POST['tutorGroup']);
        $courseID = sanitizeInput($_POST['courseID']);
        $description = sanitizeInput($_POST['desc']);
        $courseYear = date("Y");
        $website = sanitizeInput($_POST['website']);
        $skillSets = sanitizeInput($_POST['skillSets']);
        $specialisation = sanitizeInput($_POST['specialisation']);
        $photo = sanitizeInput($_POST['photo']);

        // this is what i tried, checking if the value entered is empty, but doesn't work
        if($photo = ""){
            $photo="images/avatarDefault.png";
        }

        $resume = sanitizeInput($_POST['resume']);

        //Validation for Username
        $sql = "SELECT * FROM Users WHERE UserID= '$username'";
        if (mysqli_num_rows(mysqli_query($con,$sql)) > 0){
            echo 'User already exists! Please Change the Username!<br>';
            $valid = false;
        }

        if($valid){
            //Incomplete SQL Query
            $sql = "INSERT INTO Users
             VALUES ('$username','$displayname','$hashed_password','$type','$email', '$tutorGroup', ";

            //Conditionally Concatenate Values
            if(empty($courseID))
            {
                $sql = $sql . "NULL";
            }
            else
            {
                $sql = $sql . " '$courseID' ";
            }

            //Completed SQL Query
            $sql = $sql . ", '$description', '$skillSets', '$specialisation', '$website', '$courseYear', '$photo',  '$resume', DEFAULT)";

            //retval from the SQL Query
            if (!mysqli_query($con,$sql))
            {
                echo '*Error*: '. mysqli_error($con);
            }
            else
            {
                echo "*Success*: User Added!";
            }
        }

        //if student create folder for them
        if ($type == 'B')
        {
            //Store current reporting error
            $oldErrorReporting = error_reporting();

            //Remove E_WARNING from current error reporting level to prevent users from seeing code
            error_reporting($oldErrorReporting ^ E_WARNING);

            //Set current reporting error();
            error_reporting($oldErrorReporting);
        }

        mysqli_close($con);
    }
}
function sanitizeInput($data)
{
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}
?>
 
 我试图在mysql上找到一种方法来插入默认值，但似乎不可能，所以我别无选择，只能通过php查询插入。 
 
 我有逻辑，但我不知道如何在PHP上实现我缺乏知识，我想要检查1）如果照片链接没有单词.png / .jpg， $photo != ".png" 2）如果照片链接长度太低$.photo.length < 10 
 
 有人可以帮助我查看代码并告诉我我做错了什么？ 谢谢！ 

end web developer, i was given a CMS done from another team and i have to link with my front-end. I have made some modifications, but due to my lack of php knowledge i have some issue here. 
 
My users are able to fill up a form, where 1 text field is asking for their photo link. I want to check for if the value entered is not equal to what i want, then i will query insert a default avatar photo link to mysql to process.
 
code that i tried on php
 
// check if the variable $photo is empty, if it is, insert the default image link
if($photo = ""){
    $photo="images/avatarDefault.png";
}
 
doesn't seem to work
 
<?php
if($_SERVER["REQUEST_METHOD"] === "POST")
{
    //Used to establish connection with the database
    include 'dbAuthen.php';
    if (mysqli_connect_errno())
    {
        echo "Failed to connect to MySQL: " . mysqli_connect_error();
    }
    else
    {

        //Used to Validate User input
        $valid = true;

        //Getting Data from the POST
        $username = sanitizeInput($_POST['username']);
        $displayname = sanitizeInput($_POST['displayname']);
        $password = sanitizeInput($_POST['password']);

        //hash the password using Bcrypt - this is to prevent 
        //incompatibility from using PASSWORD_DEFAULT when the default PHP hashing algorithm is changed from bcrypt  
        $hashed_password = password_hash($password, PASSWORD_BCRYPT);

        //Determining Type of the User
        //if B - User is student
        //if A - User is adin
        if($_POST['type'] == 'true')
            $type = 'B';
        else
            $type = 'A';

        $email = sanitizeInput($_POST['email']);
        $tutorGroup = sanitizeInput($_POST['tutorGroup']);
        $courseID = sanitizeInput($_POST['courseID']);
        $description = sanitizeInput($_POST['desc']);
        $courseYear = date("Y");
        $website = sanitizeInput($_POST['website']);
        $skillSets = sanitizeInput($_POST['skillSets']);
        $specialisation = sanitizeInput($_POST['specialisation']);
        $photo = sanitizeInput($_POST['photo']);

        // this is what i tried, checking if the value entered is empty, but doesn't work
        if($photo = ""){
            $photo="images/avatarDefault.png";
        }

        $resume = sanitizeInput($_POST['resume']);

        //Validation for Username
        $sql = "SELECT * FROM Users WHERE UserID= '$username'";
        if (mysqli_num_rows(mysqli_query($con,$sql)) > 0){
            echo 'User already exists! Please Change the Username!<br>';
            $valid = false;
        }

        if($valid){
            //Incomplete SQL Query
            $sql = "INSERT INTO Users
             VALUES ('$username','$displayname','$hashed_password','$type','$email', '$tutorGroup', ";

            //Conditionally Concatenate Values
            if(empty($courseID))
            {
                $sql = $sql . "NULL";
            }
            else
            {
                $sql = $sql . " '$courseID' ";
            }

            //Completed SQL Query
            $sql = $sql . ", '$description', '$skillSets', '$specialisation', '$website', '$courseYear', '$photo',  '$resume', DEFAULT)";

            //retval from the SQL Query
            if (!mysqli_query($con,$sql))
            {
                echo '*Error*: '. mysqli_error($con);
            }
            else
            {
                echo "*Success*: User Added!";
            }
        }

        //if student create folder for them
        if ($type == 'B')
        {
            //Store current reporting error
            $oldErrorReporting = error_reporting();

            //Remove E_WARNING from current error reporting level to prevent users from seeing code
            error_reporting($oldErrorReporting ^ E_WARNING);

            //Set current reporting error();
            error_reporting($oldErrorReporting);
        }

        mysqli_close($con);
    }
}
function sanitizeInput($data)
{
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}
?>
 
i've tried finding a way on mysql to insert default values but it seem impossible, so i have no choice but to query insert through php.
 
I have the logic but i'm not sure how to implement on the php with my lack of knowledge, i was thinking of checking either 1) if the photo link does not have the word .png/.jpg, $photo != ".png" 2) if the photo link length is too low $.photo.length < 10
 
can someone help me look into the code and tell me what i'm doing wrong? Thanks!

原文：https://stackoverflow.com/questions/27100528