Warning: Undefined array key in php for unknown reason

Hello everyone
I was practicing php arrays and my editor cannot detect an error I have with my php however when it runs I get the error message

Warning: Undefined array key 3 in php

while still printing the output correctly.
my html form is:

    <!DOCTYPE html>
    <html>
        <head><title>Number of Students</title></head>
        <body>
            <form action="Q4.php">
                <table>
                    <tr>
                        <td>Number of Students:</td>
                        <td><input type="text" name="num" size="5"></td>
                        <td><input type="submit" value="Submit"></td>
                    </tr>
                </table>
            </form>
        </body>
    </html>

my php form is:

    <!DOCTYPE html>
    <html>
        <head><title>Number of Students</title></head>
        <body>
            <form action="Q4index.php">
            <table border=1 cellspacing=0 cellpadding=3>
                <tr><th>Student</th><th>Mark</th></tr>
            <?php
            $num = $_GET["num"];
            for($i=1; $i<=$num; $i++){
            echo"<tr><td><input type=text name=stud[] size=7></td>
            <td><input type=text name=mark[] size=5></td></tr>";
            }
            ?>
            <tr><td><input type="submit" value="Submit"></td><td><input type="Reset" value="Reset"</td></tr>
            </table>
            </form>
        </body>
    </html>

and the php program file to run it all is:

    <!DOCTYPE html>
    <html>
        <head><title></title></head>
        <body>
            <h3>The students who passed the exam:</h3>
            <table border="1" cellspacing="0" cellpadding="3">
                <tr><th>Name</th><th>Total Mark</th></tr>
            <?php
            //Declaration of Arrays
            $name=$_GET["stud"];
            $mark=$_GET["mark"];
            //Loop and Conditions
            for($i=0; $i<=count($name); $i++){ 
                if($mark[$i]>=50){
            //Printing        
                echo"<tr><td>$name[$i]</td><td>$mark[$i]</td></tr>";}
            }
            ?>
            </table>
        </body>
    </html>

After entering sample data in the forms and trying to execute the code this error message appears: Screenshot of error
Can someone please tell me what my code is missing? Thank you in advance and I’m beyond grateful for your patience with my questions 🙂

Answer

Remove ‘=’ in condition “$i<=count($name)”. Write “$i < count($name)”.

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Answer