Basic PHP Function. Please help

egregious

Que :- Create an associative array with a few countries as indexes(keys) and their respective capitals as values. Create a function which takes the country name as argument and returns it's capital city.

Here's the code that I wrote :-

<html>
<head>
<title> Function</title>
</head>
<body>
<?php
function capitalof ($country)                                 //creating the function 'capitalof'
{
   $capital=array( );
   $ans;
   foreach ($capital as $key => $value)
   {
      if ($key==$country)
      {
         $ans=$value;
   }
}
return $ans;                                                  //returns the value of the index
}
$capitals["FRANCE"]="Paris";
$capitals["PAKISTAN"]="Islamabad";
$capitals["ITALY"]="Rome";
$capitals["ENGLAND"]="London";                               //defining associative array
$capitals["GERMANY"]="Berlin";
$capitals["USA"]="Washington";
$capitals["EGYPT"]="Cairo";
$capitals["SWITZERLAND"]="Bern";
foreach ($capitals as $key => $value)
{
   echo ("<h1>Capital of $key is $value</h1>");               //printing each values with their respective indexes             

   }                                                     

$cap=capitalof("FRANCE");                                       //using 'capitalof' to get the capital of India
echo ("<h1>Using function, France's capital is $cap</h1>");      

?>
</body>
</html>

I am getting the output while not using the function 'capitalof'. But I can't seem to understand why no output whilst the function is being used.

But when I put the array inside the function, I am getting the result :-

<html>
<head>
<title>Function</title>
</head>
<body>
<?php
function capitalof($country)                                      //creating the function 'capitalof'
{
   $capitals["FRANCE"]="Paris";
   $capitals["PAKISTAN"]="Islamabad";
   $capitals["ITALY"]="Rome";
   $capitals["ENGLAND"]="London";                                //defining associative array
   $capitals["GERMANY"]="Berlin";
   $capitals["USA"]="Washington";
   $capitals["EGYPT"]="Cairo";
   $capitals["SWITZERLAND"]="Bern";
   $ans;
   foreach ($capitals as $key => $value)
   {
      if ($key == $country)
      {
         $ans = $value;
      }
   }
   return $ans;                                                  //returns the value of the index
}
$capitals["FRANCE"]="Paris";
$capitals["PAKISTAN"]="Islamabad";
$capitals["ITALY"]="Rome";
$capitals["ENGLAND"]="London";                                    //defining associative array
$capitals["GERMANY"]="Berlin";
$capitals["USA"]="Washington";
$capitals["EGYPT"]="Cairo";
$capitals["SWITZERLAND"]="Bern";
foreach ($capitals as $key => $value)
{
   echo ("<h1>Capital of $key is $value</h1>");                  //printing each values with their respective indexes             

} 
$cap = capitalof("FRANCE");                                       //using 'capitalof' to get the capital of India
echo ("<h1>Using function, France's capital is $cap</h1>");
?>
</body>
</html>

If I take out the index France from the function, it doesn't work while executing. No errors mentioned. I can't seem to figure out why. Can someone help me?

bradgrafelman

Take a look at your function:

function capitalof ($country)                                 //creating the function 'capitalof' 
{ 
   $capital=array( ); 
   $ans; 
   foreach ($capital as $key => $value) 
   { 
      if ($key==$country) 
      { 
         $ans=$value; 
   } 
} 
return $ans;                                                  //returns the value of the index 
}

It doesn't really make sense; you define $capital as an empty array, and then you try to use a [man]foreach[/man] loop on that empty array.

EDIT: If you're expecting to use anything inside of that function that is defined elsewhere (such as an array called $capitals), then you need to pass it into the function as a parameter.

egregious

bradgrafelman;10996888 wrote:
Take a look at your function:
function capitalof ($country)                                 //creating the function 'capitalof' 
{ 
   $capital=array( ); 
   $ans; 
   foreach ($capital as $key => $value) 
   { 
      if ($key==$country) 
      { 
         $ans=$value; 
   } 
} 
return $ans;                                                  //returns the value of the index 
} 
It doesn't really make sense; you define $capital as an empty array, and then you try to use a [man]foreach[/man] loop on that empty array.

EDIT: If you're expecting to use anything inside of that function that is defined elsewhere (such as an array called $capitals), then you need to pass it into the function as a parameter.

Okay. I was taught that the function 'array()' can be used to create an array like in C programming.
I can't pass it into the function as a parameter. My function should take only one argument and that is the index of the array (in this case, the country name)

bradgrafelman

egregious;10996890 wrote:
Okay. I was taught that the function 'array()'

That's not a function - it's a PHP language construct. See the manual page for the variable type [man]array[/man].

egregious;10996890 wrote:
can be used to create an array like in C programming.

It does indeed return an empty array; as I noted above, this is actually your problem. You're creating an empty array, and then you're trying to loop over its elements as if it contains something, when in fact it obviously does not.

egregious;10996890 wrote:
I can't pass it into the function as a parameter. My function should take only one argument and that is the index of the array (in this case, the country name)

Why can't you pass it in as a parameter? What good is passing in the index of the array if the function doesn't actually get passed the array itself?

egregious

bradgrafelman;10996892 wrote:
That's not a function - it's a PHP language construct. See the manual page for the variable type [man]array[/man].

It does indeed return an empty array; as I noted above, this is actually your problem. You're creating an empty array, and then you're trying to loop over its elements as if it contains something, when in fact it obviously does not.

Why can't you pass it in as a parameter? What good is passing in the index of the array if the function doesn't actually get passed the array itself?

I'm sorry. It's been a just a few days since I started learning PHP. I don't get what do you mean by passing it in as a parameter?

In the 2nd code of my first post, I used the same array inside the function and I am getting the result. When I erase the index France and it's value from within the function (but it remains inside the main php code) I am not getting the result.

Weedpacket

Your loop is entirely unnecessary anyway: [man]array_key_exists[/man] (although, unless you're going to include Antarctica as a country, [man]isset[/man] is enough).

bradgrafelman

egregious;10996893 wrote:
I don't get what do you mean by passing it in as a parameter?

I mean passing the array in as a second parameter just like you're already doing with the index as the first parameter. See the manual page [man]functions.arguments[/man] for more info.

egregious;10996893 wrote:
In the 2nd code of my first post, I used the same array inside the function

No you didn't, you used an array that is much differen than the first one in that the array in the second version actually has data in it.

In other words, in the first code snippet your array is this:

$capital=array( );

whereas the second time the array is constructed by this:

   $capitals["FRANCE"]="Paris"; 
   $capitals["PAKISTAN"]="Islamabad"; 
   $capitals["ITALY"]="Rome"; 
   $capitals["ENGLAND"]="London";                                //defining associative array 
   $capitals["GERMANY"]="Berlin"; 
   $capitals["USA"]="Washington"; 
   $capitals["EGYPT"]="Cairo"; 
   $capitals["SWITZERLAND"]="Bern";

Weedpacket

egregious wrote:
I'm sorry. It's been a just a few days since I started learning PHP. I don't get what do you mean by passing it in as a parameter?

The question is why you can't write

function capitalof($array_of_country_capital_pairs, $country)
{
//...
}

and

$capital_of_France = capitalof($countries, 'France');

The question is asked because there are ways of working around it, but which is appropriate depends on why the workaround is necessary in the first place.

egregious

bradgrafelman;10996895 wrote:
I mean passing the array in as a second parameter just like you're already doing with the index as the first parameter. See the manual page [man]functions.arguments[/man] for more info.

No you didn't, you used an array that is much differen than the first one in that the array in the second version actually has data in it.

In other words, in the first code snippet your array is this:
$capital=array( ); 
whereas the second time the array is constructed by this:
   $capitals["FRANCE"]="Paris"; 
   $capitals["PAKISTAN"]="Islamabad"; 
   $capitals["ITALY"]="Rome"; 
   $capitals["ENGLAND"]="London";                                //defining associative array 
   $capitals["GERMANY"]="Berlin"; 
   $capitals["USA"]="Washington"; 
   $capitals["EGYPT"]="Cairo"; 
   $capitals["SWITZERLAND"]="Bern";

I meant that the array inside the function the one below it in the 2nd code is same. I get it why 'array()' of my first code is totally wrong.

I passed the array as an argument together with the key and now I am getting the result . Here's my new code :-

<html>
<head>
<title>Function</title>
</head>
<body>
<?php
function capitalof($array,$country)                                      //creating the function 'capitalof'
{

 foreach ($array as $key => $value)
   {
      if ($key == $country)
      {
         $ans = $value;
      }
   }
   return $ans;                                                  //returns the value of the index
}
$capitals["FRANCE"]="Paris";
$capitals["PAKISTAN"]="Islamabad";
$capitals["ITALY"]="Rome";
$capitals["ENGLAND"]="London";                                    //defining associative array
$capitals["GERMANY"]="Berlin";
$capitals["USA"]="Washington";
$capitals["EGYPT"]="Cairo";
$capitals["SWITZERLAND"]="Bern";
foreach ($capitals as $key => $value)
{
   echo ("<h1>Capital of $key is $value</h1>");                  //printing each values with their respective indexes             

} 
$cap = capitalof($capitals,"FRANCE");                                       //using 'capitalof' to get the capital of India
echo ("<h1>Using function, France's capital is $cap</h1>");
?>
</body>
</html>

But the thing is I am asked to take only one argument inside my function and that is the key name only.

egregious

Weedpacket;10996896 wrote:
The question is why you can't write
function capitalof($array_of_country_capital_pairs, $country)
{
//...
}
and
$capital_of_France = capitalof($countries, 'France');
The question is asked because there are ways of working around it, but which is appropriate depends on why the workaround is necessary in the first place.

Yes, it works for me 🙂 Thanks

But I am asked to take only one argument inside my function - the key name. ($country alone)

Weedpacket

egregious wrote:
But I am asked to take only one argument inside my function - the key name. ($country alone)

Any technical reason for this? (Is there, for that matter, any technical reason for the function; as opposed to, say,

$capital = @$lookup_capitals['France'] ?: null;

johanafm

Weedpacket;10996901 wrote:
Any technical reason for this? (Is there, for that matter, any technical reason for the function; as opposed to, say,
$capital = @$lookup_capitals['France'] ?: null;
?)

I'd prefer writing that as

$capital = isset($lookup_capitals['France']) ? $lookup_capitals['France'] : null;

instead of getting into the habit of using the error supression operator like it's a good thing. Sooner or later a country that should be there with its capital seems to be missing. Without error supression they'd get information about undefined index.

Weedpacket

johanafm wrote:
using the error supression operator like it's a good thing.

I don't use it either on aesthetic grounds (but note that your replacement has exactly the same behaviour, so to have complaints about the behaviour that results when it is not used seems like an odd reason to not use it).

In hindsight

$capital = $lookup_capitals['France'] ?: null;

more closely mimics the desired behaviour of the original function, since that will generate notices whenever a bogus country is given (assuming the array ever gets suitably populated). So given the operator, why the function?

Derokorian

function capitalof($array,$country)                                      //creating the function 'capitalof'
{
   foreach ($array as $key => $value)
   {
      if ($key == $country)
      {
         $ans = $value;
      }
   }
   return $ans; 
}

This is still over kill, you could simply do:

function capitalof($array,$country)                                      //creating the function 'capitalof'
{
   return isset($array[$country]) ?: NULL;
}

Weedpacket

And if you don't want to pass the array as a parameter....

function capitalof($country)
{
   static $countries_and_capitals = array(
      'France' => 'Paris',
      //...
   );
    return isset($countries_and_capitals[$country]) ? $countries_and_capitals[$country] : null; 
}

Derokorian wrote:
This is still over kill, you could simply do:
   return isset($array[$country]) ?: NULL; 

Actually, that still cause me to double-take on occasion: that won't actually return $array[$country].

Derokorian

Weedpacket;10996937 wrote:
Actually, that still cause me to double-take on occasion: that won't actually return $array[$country].

Ugh, good point it will return true if isset is true and null if its not...

traq

this sounds like a homework assignment to me...

Derokorian: it's not really broken

return isset($array[$country]) ? $array[$country]: NULL;

Derokorian

Never said it was broken, I just always forget that isset doesn't return the variable when set, and skipping the middle part of ternary is the same as saying return the result of the logical statement.

egregious

traq;10996941 wrote:
this sounds like a homework assignment to me...

Derokorian: it's not really broken
return isset($array[$country]) ? $array[$country]: NULL; 

homework assignment for those who are experts.

traq

egregious;10996982 wrote:
homework assignment for those who are experts.

no, I don't mean that it's "simple" or "obvious to anyone who's not in school," I mean that this:

egregious wrote:
Create an associative array with a few countries as indexes(keys) and their respective capitals as values. Create a function which takes the country name as argument and returns it's capital city.

literally sounds like a homework assignment.

i.e., a question copied off of an assignment sheet.

The further restrictions (only one argument, etc.), for which you offer no real explanation beyond "that's what you're asked to do," lends support to this conclusion.

I'm not saying it's "bad" if this is a homework assignment. if it is, then I would suggest that you won't learn anything as a result of copy-and-pasting anyone's suggestions.