PHP - Undefined variable although the variable is globally defined

Question

Why does this code give a Undefined variable : $category_id

// declare a variable and an array
$category_id;
$posts = [];

// get four categories
$categories = Category::take(4)->get();

foreach($categories as $category){
  //foreach of the four categories, get the category id
  $category_id = $category->$category_id;

  //add three posts of each of those categories to the $posts array
  $posts[] = Category::where('category_id', $category_id)->take(3)->get();

}

Althought I defined the variable on the top as $category_id;. why does the error persist?
Is it something to do with the $category->$category_id skewing the code?

the $category->$category_id; has a value, but the error is on the " $category_id = " s $category_id. Why is that? — JGCW
– JGCW, Commented Dec 10, 2015 at 5:58
On which line are you getting the above error !!, things seem to fine in the code — sanjeev
– sanjeev, Commented Dec 10, 2015 at 6:01

VolkerK · Accepted Answer · 2015-12-10 06:15:32Z

3

$category_id = $category->$category_id;

is most likely wrong, you probably mean

$category_id = $category->category_id;

and you should (again: most likely) initialize the variable by assigning a literal value or constant or similar, e.g.

// declare a variable and an array
$category_id=null;

(edit: or leave that initialisation out completely. In the code snippet you've posted, $category_id is used only when it obviously has been assigned a value within the loop and it looks like you're not preserving the variable for use after the foreach loop.)

edited Dec 10, 2015 at 6:15

answered Dec 10, 2015 at 6:11

VolkerK

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Comments

SIDU · Accepted Answer · 2015-12-10 05:49:26Z

0

I never declare a variable without anything following like yours above before.

what about:

$category_id = null;

answered Dec 10, 2015 at 5:49

SIDU

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4 Comments

JGCW Over a year ago

i want an explanation why this is happening.

SIDU Over a year ago

I m not sure if it is legal to declare a variable by just write its name, nothing else?

VolkerK Over a year ago

"$category_id = null;" - But then again what would $category->{null} be?

SIDU Over a year ago

now i see the problem. you need to have initial value for the first id: $category_id = $category->$category_id; why the second has $, is it a typo?

shailesh · Accepted Answer · 2017-02-04 09:44:30Z

<form method="post" action="convert1.php">
hour  :  <input type="hour" name="fhour"><br><br>
minute:<input type="minute" name="fminute"><br><br>
second: <input type="second" name="fsecond"><br><br>
month:<input type="text" name="fmonth"><br><br>
day:<input type="day" name="fday"><br><br>
year : <input type="text" name="fyear"><br><br>
date :  <input type="date" name="fdate"><br><br>

<input type="submit" name="submit" value="submit" >
</form>


<?php
if(isset($_POST['submit']))
    //print_r($_POST);
{



    $hour=$_REQUEST['fhour'];
    $minute=$_REQUEST['fminute'];
    $second=$_REQUEST['fsecond'];
    $month=$_REQUEST['fmonth'];
    $day=$_REQUEST['fday'];
    $year=$_REQUEST['fyear'];
    $date=$_REQUEST['fdate'];

    $timestamp = mktime($fhour, $minute, $second, $month, $day, $year,$date);
    //date('r', $timestamp);
    echo 'timestamp in second='.$timestamp;
    echo $minute=$timestamp/60;
    echo '<br>';
    echo $second=$timestamp/24;
    echo'<br>';
    echo $milisecond=$timestamp*100;
    echo '<br>';

}   
?>
please solution

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